Variable transmittance optical filter with substantially co-planar electrode system

ABSTRACT

A variable transmittance optical filter comprising: a first layer comprising a first substantially transparent substrate with a substantially co-planar (SC) electrode system disposed thereon, the SC electrode system made of transparent electrically conductive material and comprising at least one pair of electrically separate electrodes arranged in a substantially co-planar manner on the first substantially transparent substrate, each pair of electrically separate electrodes comprising a first electrode and a second electrode, a second layer proximate to the first layer and comprising a transition material that darkens in response to a non-electrical stimulus and lightens in response to application of an electric voltage; and an electrical connection system for electrically connecting the SC electrode system to a source of electric voltage.

RELATED CASES

This application claims the benefit of U.S. Provisional Application No.61/423,536 filed Dec. 15, 2010, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of variable transmittanceoptical filters, in particular to those comprising an optical filtercapable of transitioning from one state of visible light transmittanceto another with application of an electric voltage to a substantiallyco-planar electrode system.

BACKGROUND OF THE INVENTION

Optical filters are widely used to control visible and solar energy.Most notably, optical filters have been used as glazings in windowtechnology (e.g. windows of buildings, vehicles, aircraft, spacecraft,ships or the lie) to control the flow of light and heat into and out ofthe glazing, for glare reduction and energy load management. Improvingthe energy efficiency of buildings is a key aspect of reducing energyuse and reducing CO₂ emissions. Buildings consume about 39% of allenergy and 68% of the electricity used in the United States, and areresponsible for about 38% of all greenhouse gas (GHG) emissions. Windowsare responsible for about 30% of a buildings energy loss. As such,windows with improved technology for reducing heat loss and solar heatgain can offer significant benefits and cost savings.

Optical filters (“tinted windows”) may be used in vehicle windows toprovide privacy for occupants, prevent glare and/or reduce solar heatgain without sacrificing visibility. Static tints generally cannot bealtered, and if further ‘darkening’ is desired, a blind may bedrawn—eliminating any visibility for the occupants. ‘Panoramic’ sunroofsmay be installed to provide visibility to occupants (e.g. forsightseeing—‘dome roofs’) and provide a feeling of ‘being outside’, adrawn blind does not accommodate this desire, and for a large roof ordome, may be difficult for a user to manipulate at will.

Optical filters have also found application in ophthalmic devices tocontrol the light impacting the eye. Applications include, for example,prescription and nonprescription glasses, goggles, sunglasses, visors,and safety eyewear.

There are a number of technologies that have been used in optical filterapplications for dynamically varying the degree of visible lighttransmittance, including photochromics, electrochromics, liquidcrystals, thermochromics, and suspended particle displays.

Some optical filters used in window applications requiring theapplication of electrical voltage to vary the degree of visible lighttransmittance—such devices typically comprise two transparent conductiveelectrodes on opposing substrates to which the electrical voltage isapplied. These transparent conductive electrodes can be formed using aconductive coating such as indium-tin oxide (ITO) on glass or polymericfilm. A material that transitions from one state of visible lighttransmittance to another upon the application of electrical voltage issandwiched between the two transparent conductive electrodes. Forexample, electrochromic technology involves applying thin coatings ofelectrochromic materials to two transparent conductive electrodes andsandwiching an electrolyte material in between. Electrochromictechnology typically requires the user to apply external electricalpower to darken. Electrochromic technology is used in auto-dimmingautomobile mirrors (for example, those made by Gentex Corporation ofZeeland Mo.).

Another example of electrochromics is in window applications (SageElectrochromics Inc. of Faribault, Minn.) that incorporate thin coatingsapplied to one of the glass layers in a window. Application ofelectricity with the positive lead connected to one electrode causes thewindow to darken, and application of electricity with the positive leadconnected to the other electrode causes the window to lighten. Theelectrochromic coating that is applied to the glass involves the use ofspecialized coating processes such as sputtering and chemical vapordeposition. This often requires a specialized factory or facilityrequiring the glass to be shipped to one central factory for the coatingprocess to be performed, and then shipped out to wherever they will beused. As such, windows made using electrochromic technology can be quiteexpensive. This type of window system also employs an electrode systemwith two conductive transparent electrodes on opposing substrates.

Electrochromics have also been used in ophthalmic devices. For example,ChromoGenics of Uppsala, Sweden makes an “electrochromic foil” for usein motorcycle helmet visors and other products by making a multi-layerelectrochromic device between two plastic films. Relatively low DCvoltages are used for switching the electrochromics from one state toanother but power is typically required to maintain the electrochromicdevice in the dark state. These electrochromic foils also utilize anelectrode system with two conductive transparent electrodes on opposingsubstrates.

Patterning of ITO (indium tin oxide) has been used to prepare for liquidcrystal displays and touch panels. The objective of patterning the ITOin these cases is to create an array of pixels such that each pixel canbe uniquely addressed and either turned on or off or a touch detected,depending on the application.

Interdigitated electrodes have been described in the design of organicelectrochromic devices with three-electrode dynamic operation fordisplay technology (Galit Bar et al., “A new approach for design oforganic electrochromic devices with interdigitated electrode structure,”Solar Energy Materials & Solar Cells (2009) 93:2118-2124)).

U.S. Pat. No. 7,323,634 describes a method of forming an electroniccircuit component using the technique of drop on demand printing todeposit droplets of deposition material, the method comprisingdepositing a plurality of droplets on a surface to form a patternedelectronic device comprising multiple discrete portions.

United States Patent Publication No. 20070128905 describes transparentelectrical conductors comprising regions of high transparency andregions of lower transparency, but higher conductivity. This allowselectrical connection through the conductor, while retaining itstransparency for such applications as hand-held device display screensor transparent antennas, for example.

United States Patent Publication No. 20070153355 describes anelectrochromic film and demonstrates the electrochromic effect of asingle substrate film by applying electronic current to induce areversible oxidation-reduction reaction of an organic electrochromiclayer. The electrochromic film can attach to a surface of an object withthe use of an adhesive layer.)

U.S. Pat. Nos. 6,597,489 and 6,606,184 describe an electrode device foran electrochromic device, where the electrodes are disposed on asubstrate in a substantially coplanar relation. An electrochromic mediumcomprising a cathodic and an anodic species, at ratio within theelectrochromic medium in relation to the surface areas of the positiveand negative electrodes is described.

SUMMARY OF THE INVENTION

The present invention relates to variable transmittance optical filters,more particularly those comprising a co-planar, or substantiallyco-planar electrode, and capable of transitioning from a firsttransmittance state to a second transmittance state with application) ofan electric voltage.

In accordance with one aspect of the invention, there is provide avariable transmittance optical filter comprising: a) a first layercomprising a first substantially transparent substrate with asubstantially co-planar (SC) electrode system disposed thereon, the SCelectrode system made of transparent electrically conductive materialand comprising at least one pair of electrically separate electrodesarranged in a substantially co-planar manner on the first substantiallytransparent substrate, each pair of electrically separate electrodescomprising a first electrode and a second electrode, b) a second layerproximate to the first layer and comprising a transition material thatdarkens in response to a non-electrical stimulus and lightens inresponse to application of an electric voltage; and c) an electricalconnection system for electrically connecting the SC electrode system toa source of electric voltage.

In accordance with another aspect of the invention, there is provided avariable transmittance optical filter comprising: a) a first layercomprising a first substantially transparent substrate with asubstantially co-planar (SC) electrode system disposed thereon, the SCelectrode system made of transparent electrically conductive materialand comprising at least one pair of electrically separate electrodesarranged in a substantially co-planar manner on the first substantiallytransparent substrate, each pair of electrically separate electrodescomprising a first electrode and a second electrode, b) a second layerproximate to the first layer and comprising a transition material thatis capable of dynamically varying the degree of visible lighttransmittance on application of an electric voltage; and c) anelectrical connection system for electrically connecting the SCelectrode system to a source of electric voltage, wherein after apositive voltage is applied to the first electrode and a negativevoltage is applied to the second electrode, the polarity of the voltageapplied to the first electrode and the second electrode is alternatelyreversed one or more times to transition the transition a first state ofvisible light transmittance to a second state of visible lighttransmittance.

In accordance with another aspect of the invention, there is provided avariable transmittance optical filter comprising: a) a first layercomprising a first substantially transparent substrate with asubstantially co-planar (SC) electrode system disposed thereon, the SCelectrode system made of transparent electrically conductive materialand comprising two or more pairs of electrically separate electrodesarranged in a substantially co-planar manner on the first substantiallytransparent substrate, each pair of electrically separate electrodescomprising a first electrode and a second electrode, b) a second layerproximate to the first layer and comprising a transition material thatis capable of dynamically varying the degree of visible lighttransmittance on application of an electric voltage; and c) anelectrical connection system for electrically connecting the SCelectrode system to a source of electric voltage.

In accordance with another aspect of the invention, there is provided amethod of preparing a variable transmittance optical filter comprisingthe steps of: providing a first layer comprising a first substantiallytransparent substrate with a substantially transparent, electricallyconductive material disposed thereon; etching into the electricallyconductive material a substantially co-planar (SC) electrode system, theSC electrode system comprising at least one pair of electricallyseparate electrodes arranged in a substantially co-planar manner, eachpair of electrically separate electrodes comprising a first electrodeand a second electrode; disposing a second layer proximate to the SCelectrode system, the second layer comprising a transition material thatis capable of dynamically varying the degree of visible lighttransmittance on application of an electric voltage; and providing anelectrical connection system electrically connecting the SC electrodesystem to a source of electric voltage.

In accordance with another aspect of the invention, there is provided amethod of preparing a variable transmittance optical filter comprisingthe steps of: providing a first layer comprising a first substantiallytransparent substrate; printing onto the first substrate a substantiallyco-planar (SC) electrode system using a conductive ink, the SC electrodesystem comprising at least one pair of electrically separate electrodesarranged in a substantially co-planar manner, each pair of electricallyseparate electrodes comprising a first electrode and a second electrode;disposing a second layer proximate to the SC electrode system, thesecond layer comprising a transition material that is capable ofdynamically varying the degree of visible light transmittance onapplication of an electric voltage; and providing an electricalconnection system electrically connecting the SC electrode system to asource of electric voltage.

In accordance with another aspect of the invention, there is provided amethod of transitioning a transition material from a dark state to afaded state comprising the steps of: applying a positive voltage to afirst electrode and a negative voltage to a second electrode; reversingthe polarity of the voltage, thereby applying a negative voltage to thefirst electrode and a positive voltage to the second electrode. Invarious aspects, the polarity of the voltage may be reversed once, ormore than once.

In various embodiments, the voltage applied to the first and secondelectrodes is from about 0.5 to about 3.0 V, or from about 1.2V to about2.5 V, or from about 1.8V to about 2.2 V, or any amount or rangetherebetween.

In various aspects, the variable transmittance optical filter furthercomprises a third layer comprising a second substantially transparentsubstrate.

In various aspects, the first and second electrodes may each comprisefinger-like structures, and may be interdigitated. The finger-likestructures may be substantially the same length. The fingerlikestructures may form a linear or curvilinear unit. The fingerlikestructures may have an interdigit spacing of from about 10 μm to about 1mm or any amount or range therebetween.

In various aspects, the width of the fingerlike structures of the firstelectrode may be the same, or substantially the same, as the width ofthe fingerlike structures of the second electrode. The surface area ofthe first electrode may be substantially the same as the surface area ofthe second electrode.

In various aspects, the width of the fingerlike structures of the firstelectrode may be greater than the width of the fingerlike structures ofthe second electrode. The surface area of the first electrode may begreater than the surface area of the second electrode. The ratio of thewidth of the first electrode to the second electrode is from about 2:1to about 100:1 or any amount or range therebetween. The first electrodeand the second electrode may have a relative area of about 2:1 to about1000:1 or any amount or range therebetween.

In various aspects the first electrode may be an anode, and the secondelectrode a cathode. In other aspects, the first electrode may be acathode and the second electrode an anode.

In various aspects, the transition material may comprise a hybridphotochromic/electrochromic (hybrid P/E) compound. The hybrid P/Ecompound may be organic. The hybrid P/E compound may be an anodicspecies. The hybrid P/E compound may be selected from the groupcomprising diarylethenes, dithienylcyclopentenes and fulgides. Thenon-electrical stimulus may be light. The light may comprise wavelengthsof about 350 to about 420 nm, or of about 365 to about 420 nm, or ofabout 375 to about 420 nm, or of about 375 to about 420 nm, or of about380 to about 420 nm, or of about 385 nm to about 420 nm, or any amountor range therebetween.

In various aspects the first substantially transparent substrate and thesecond substantially transparent substrate are independently rigid orflexible, and may each independently be glass or a thermoplasticpolymer.

In various aspects, the variable transmittance optical filters may be afilm, and may comprise part of an architectural window, a vehicle (e.g.automotive) window, an opthalmic device, or the like.

This summary of the invention does not necessarily describe all featuresof the invention. Other aspects, features and advantages of the presentinvention will become apparent to those of ordinary skill in the artupon review of the following description of specific embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will become more apparent inthe following detailed description in which reference is made to theappended drawings.

FIG. 1 is a schematic top view of a symmetric interdigitated electrodestructure, according to some embodiments of the invention.

FIG. 2 is a cross sectional schematic diagram along line E-E of thevariable transmittance optical filter with SC electrode system of FIG.1, according to some embodiments of the invention.

FIG. 3 is a schematic of an interdigitated “jelly roll” electrodepattern, according to some embodiments of the invention.

FIG. 4 is a schematic top view of an asymmetric interdigitated electrodestructure according to some embodiments of the invention.

FIG. 5 is a schematic diagram showing a multi-level interdigitatedpattern that can be used according to some embodiments of the invention.

FIG. 6 illustrates a schematic diagram showing an interdigitatedelectrode in a “jelly roll” pattern, combined with straight finger-likestructures, according to some embodiments of the invention.

FIG. 7 is a schematic view of an interdigitated “jelly roll” patternshowing multiple levels of interdigitation, according to someembodiments of the present invention.

FIG. 8 illustrates an exemplary control circuit configuration for usewith a variable transmittance optical filter according to someembodiments of the present invention.

FIG. 9 illustrates a circumferential layout of electrode configuration,according to some embodiments of the invention.

FIG. 10 shows an opthalmic device comprising a circumferential electrodelayout as illustrated in FIG. 9, according to some embodiments of theinvention.

FIG. 11 shows a photograph of devices with asymmetric electrodes,according to some embodiments of the invention. Device numbers areindicated adjacent to the devices.

FIG. 12 is a graph showing the absorbance spectra of the hybridphotochromic/electrochromic switching material according to Formulation#2 comprising hybrid P/E compound 5054 (in triglyme). Faded state (solidline); darkened using a 365 nm light source without (open circle) orwith (open square) EnergyFilm™; and darkened using a solar simulatorwithout (solid circle) or with (solid square) EnergyFilm™.

DESCRIPTION OF THE INVENTION

The present invention relates, in part, to a variable transmittanceoptical filter (“optical filter”, “filter” or “VTOF”) that is capable oftransitioning from one state of visible light transmittance to anotherwith the application of an electric voltage. The variable transmittanceoptical filter comprises a first layer comprising a substantiallytransparent substrate (a “substrate” or a “first substrate”) with asubstantially co-planar (SC) electrode system disposed thereon, a secondlayer proximate to, for example in contact with, the first layer andcomprising a transition material that is capable of dynamically varyingthe degree of visible light transmittance (VLT), and an electricalconnection system for electrically connecting the SC electrode system toa source of electric voltage. The variable transmittance optical filtermay optionally comprise a third layer having a substantially transparentsubstrate (a “second substrate”).

The SC electrode system is made of transparent electrically conductivematerial that can be adhered to or etched in a layer on thesubstantially transparent substrate. The SC electrode system comprisesat least one pair of electrically separate electrodes arranged in asubstantially co-planar manner on the substantially transparentsubstrate. Each pair of electrodes comprises a first electrode and asecond electrode (collectively, “electrodes”). In operation, a positivepotential may be applied to either the first or the second electrode,and a negative potential applied to the remaining electrode. Anelectrode to which a positive potential is applied may be referred toherein as an anode; an electrode to which a negative potential isapplied may be referred to herein as a cathode. In some embodiments, theSC electrode system comprises more than one pair of electricallyseparate electrodes arranged in a substantially co-planar manner on thesubstantially transparent substrate. In some embodiments, theapplication of voltage can be reversed in polarity one or more times inorder to facilitate transition of the transition material from one stateof visible light transmittance to another. In some embodiments, thefirst electrode is an anode and the second electrode is a cathode; insome embodiments, the first electrode is a cathode and the secondelectrode is an anode; in some embodiments, reversal of polarity mayapply an opposite charge to the first or the second, or the first andthe second electrode.

In embodiments of the present invention, two electrodes may besubstantially co-planar, in that they both reside in a first layer ofmaterial or space, while the transition material generally resides in asecond, adjacent layer of space or material. The layers may be flat, ormay comprise one or more curves. One or more, but not necessarily all,two-dimensional cross sections taken through the first layer containsportions of both the electrodes—see, for example, FIGS. 1 and 2. As anexample, two electrodes may be deemed to be substantially co-planar ifboth electrodes contact, or nearly contact, the same surface of thetransition material. The design of the electrodes of the SC electrodesystem can be varied with respect to the width or surface area of theelectrodes, the separation distance between the electrodes, the level ofinterdigitation, and characteristics of the applied voltage, such aslevel, duration, and polarity, in order to tailor the structure andfunction of the optical filter to the specific application where avariable transmittance optical filter with SC electrode system may beused. As the variable transmittance optical filter with SC electrodesystem comprises only one layer with a transparent conductive substrate,optical filters according to various embodiments of the invention are ofsimplified design, may require fewer components and may be lower in costto manufacture.

The variable transmittance optical filter with an SC electrode systemcan employ transition materials known in the art for transitioning fromone state of visible light transmittance to another with the applicationof power (a voltage) to the electrodes. Examples include, but are notlimited to, for example, electrochromic, liquid crystal, or suspendedparticle technology to enable transition from one state of visible lighttransmittance to another upon application of an electric voltage. Insome embodiments, a hybrid photochromic/electrochromic transitionmaterial exemplified herein, can be used in the variable transmittanceoptical filter.

The variable transmittance optical filter can be used in devices where atransition from one state of visible light transmittance to another uponapplication of the electric voltage is useful. Examples of such devicesinclude, for example, an optical film, an architectural window,automotive window, ophthalmic device, displays, signage, or the like.

The term “visible light” (VIS) as used herein, refers to the band ofelectro-magnetic radiation with a wavelength from about 400 nm to about750 nm. The term “ultraviolet (UV) light” as used herein, refers toelectromagnetic radiation with a wavelength shorter than that of visiblelight, or from about 10 nm to about 400 nm. In some embodiments,sub-ranges of ultraviolet light may be used, for example from about 100to about 400 nm, or from about 200 to about 400 nm, or from about 300 toabout 400 nm, or from about 350 to about 400 nm. The term “infraredradiation (IR)” as used herein, refers to electromagnetic radiation witha wavelength from about 750 nm to about 50,000 nm. Its wavelength islonger than that of visible light. Light may also be described withreference to colour or range of wavelength.

A “light source” is a source of VIS, UV and/or infrared light (IR). Alight source may also provide full spectrum light, including one or moreof VIS, UV and IR light, or light of wavelengths within a VIS, UV or IRrange. Light sources may include natural or simulated sunlight (director indirect), or light from a selected wavelength or range ofwavelengths. The selected wavelength or range of wavelengths may beselected by the nature of the light source itself (e.g. a lamp thatproduces light in a particular range such as a UV lamp, or may beselected through use of a cutoff filter, designed to eliminate lightabove or below a cutoff wavelength, or between two cutoff wavelengths.In some embodiments of the invention, the light source may be configuredto provide light above or below a predetermined wavelength, or mayprovide light within a predetermined range. A device or apparatusaccording to some embodiments of the invention may comprise a lightsource.

Devices according to various embodiments of the invention may bedescribed with reference to clarity, visible light transmittance,switching speed, durability, photostability, contrast ratio, state oflight transmittance (e.g. dark state or light state) to further definethe device, or aspects of the device; some values or characteristics ofsuch descriptors may be applicable to some or all devices, but onlyexemplified in one type of device; alternately, some values orcharacteristics of such descriptors may be applicable to only a fewtypes of devices.

“Visible light transmittance (VLT)” refers to the quantity and/orwavelength range of visible light that is transmitted or passes througha substance or product. VLT may be expressed with reference to a changein light transmission and/or a particular type of light or wavelength oflight (e.g. from about 10% visible light transmission (VLT) to about 90%VLT, or the like). A product with a higher VLT transmits more visiblelight. VLT is expressed as a number between 0 and 1, or as a percentage.VLT may alternately be expressed as absorbance, and may optionallyinclude reference to one or more wavelengths that are absorbed.According to various embodiments of the invention, a material may have acontrast ratio of at least about 2, at least about 3, at least about 4,at least about 5, at least about 6, or any amount or range therebetween.It will be appreciated by those skilled in the art that otherconfigurations of % VLT in light and dark states, and contrast ratiosthereof, may be possible with other compounds, formulations or the like.According to some embodiments, an optical filter may be selected, orconfigured to have in the dark state, a VLT of less than 80%, or lessthan 70%, or less than 60%, or less than 50%, or less than 40%, or lessthan 30%, or less than 20% or less than 10%, or any amount or rangetherebetween. According to some embodiments, an optical filter may beselected, or configured to have in the light state, a VLT of greaterthan 80%, or greater than 70%, or greater than 60%, or greater than 50%,or greater than 40%, or greater than 30%, or greater than 20% or greaterthan 10%, or any amount or range therebetween. Inclusion of a colourantor coloured film in the optical filter may additively reduce the VLT ofthe optical filter, in combination with the transition material. In someembodiments, the VLT of an optical filter in the dark state or the lightstate may independently be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16,18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90 or 95%,or any amount or range therebetween, with the proviso that the darkstate of an optical filter has lesser VLT than the light state of thesame optical filter.

The term “state of visible light transmittance” as used herein, refersto states such as a dark state, or a light state, or transition statesin between, for example. A transition material may darken (e.g. reach a‘dark state’) when exposed to light (e.g. ultraviolet light) from alight source, or when a voltage is applied, and may lighten (“fade”,“electrofade”, “bleach”, “electrobleach”, achieve a ‘light state”) whenexposed to an electric charge, or when exposed to visible light of aselected range. Such a transition material may be alternately describedas an auto-darkening material. In some embodiments, the transitionmaterial may fade upon exposure to selected wavelengths of visible (VIS)light (“photofade”, “photobleach”), without sacrifice of the ability tobe electrofaded when restored to a darkened state. This term also refersto states such as opaque, clear, translucent, or transparent. Forexample, the term “dark state” can refer to a state in which there is alow to no transmittance of visible light. The term “light state” canrefer to a state in which there is a high degree of transmittance ofvisible light. Dark state and light state may be described relative toeach other.

The contrast ratio is a ratio of the VLT of a compound or material inthe dark state and the light state. For example, a material may allowtransmission of about 10% of the visible light (10% VLT) in a darkstate, and about 60% of the visible light (60% VLT) in a faded state,providing a contrast ratio of about 6 (e.g. 6:1). According to variousembodiments of the invention, a material may have a contrast ratio of atleast about 2, or 3, or 4, or 5, or 6, or 7, or, or 9, or 10, or 11, or12, or any amount or range therebetween. It will be appreciated by thoseskilled in the art that other configurations of % VLT in light and darkstates, and contrast ratios thereof, may be possible with othercompounds, formulations or the like.

The term “mil” as used herein, refers to the unit of length for 1/1000of an inch (0.001). One (1) mil is about 25 microns; such dimensions maybe used to describe the thickness of an optical filter or components ofan optical filter, according to some embodiments of the invention.

The term “ophthalmic device” or “ophthalmics” as used herein refers to adevice placed in front of the eye to control the light impacting theeye. The term encompasses, for example, glasses (prescription andnon-prescription), goggles, sunglasses, and visors or the like.

The term “about” refers to a +/−20% variation from the nominal value. Itis to be understood that such a variation is always included in anygiven value provided herein, whether or not it is specifically referredto.

Variable Transmittance Optical Filter

The invention provides, in part a variable transmittance optical filtercomprising a first layer comprising a substantially transparentsubstrate with a substantially co-planar (SC) electrode system disposedthereon, a second layer proximate to (e.g. in contact with) the firstlayer, comprising a transition material that is capable of dynamicallyvarying the degree of visible light transmittance, and an electricalconnection system for electrically connecting the SC electrode system toa source of electric voltage.

1. First Layer and Optional Third Layer

The first layer of the variable transmittance optical filter comprises asubstantially transparent substrate with a SC electrode system disposedthereon. The variable transmittance optical filter may optionallycomprise a third layer that comprises a substantially transparentsubstrate, without an SC electrode system. Substantially transparentsubstrates suitable for use in the variable transmittance opticalfilters according to the invention are described below.

In some embodiments, the SC electrode system may be provided withoutbeing disposed on a substantially transparent substrate, if sufficientstructural integrity is provided by another layer or means. For example,the SC electrode system may comprise two or more separate electrodecomponents which may be disposed on the second layer comprising thetransition material, provided the second layer has sufficient structuralintegrity. For example, the electrode components may be applied asdecals or stickers to the second layer, or may otherwise be disposed onthe second layer via lithography, printing or other suitable methods.However, one or more substantially transparent substrates may bedesirable in embodiments of the present invention for providing rigid orflexible structural integrity, physical protection, optical filteringprotection, and the like.

1.1 Substantially Transparent Substrates

The substantially transparent substrate of the optical filter of thepresent invention provides sufficient structural integrity to supportthe SC electrode system and the transition material. Rigid or flexiblesubstrates can be used as applicable to a broad range of applications asdiscussed below. For example, variable transmittance optical filters ofthe invention that are made with a rigid substrate can operate alone ina particular application, such as a window application. Alternatively,variable transmittance optical filters of the invention that are madewith a flexible substrate can operate as a variable transmittanceoptical film that can be laminated, for example, on the selectedapplication.

Examples of suitable materials that can be used as a substrate in thepresent invention include, but are not limited to, glass andthermoplastic polymers. Suitable thermoplastic polymers includepolyesters (PE), polycarbonates, polyamides, polyurethanes,polyacrylonitriles, polyacrylacids, (e.g. poly(methacrylic acid),including polyethylene terephthalate (PET), polyolefins (PO) orcopolymers or heteropolymers of any one or more of the above, orcopolymers or blends of any one or more of the above withpoly(siloxane)s, poly(phosphazenes)s, or latex. Examples of polyestersinclude homopolymers or copolymers of aliphatic, semi-aromatic oraromatic monomeric units, for example polycondensed 4-hydroxybenzoicacid and 6-hydroxynapthalene-2-carboxylic acid (VECTRAN™), polyethylenenapthalate (PEN), polytrimethylene terephthalate (PTT), polybutyleneterephthalate (PBT), polyethylene terephthalate (PET),polyhydroxyalkanoate (PHA), polyethylene adipate (PEA), polycaprolactone(PCL) polylactic acid (PLA), polyglycolic acid (PGA) or the like.Examples of polycarbonates include bisphenol A polycarbonate or thelike. Other thermoplastic polymers include polyethene (PE),polypropylene (PP) and the like. In one embodiment of the invention, thesubstrate material is glass. In one embodiment of the invention, thesubstrate material is PET. In one embodiment of the invention, thesubstrate is heat-stabilized PET. Suitable glass includes float glass,tempered glass, laminated glass, tinted glass, mirrored glass,reinforced glass, safety glass, bullet-resistant glass, “one-way”bullet-resistance glass, Other suitable substrate materials includeceramic spinel or aluminum oxynitride. For an optical filter or a devicecomprising two or more substrates, the substrates may be the samematerial, or different. The material comprising a substrate may have UV,IR or VIS light blocking characteristics.

In a further embodiment of the invention, at least one of the substratesincorporates a UV blocker in, or on, the substrate. In embodiments ofthe invention, a UV blocker (e.g. a UV blocking layer or film applied toa substrate, or combined with material of a substrate) is provided whichblocks or reflects a portion of the incident UV light, but still allowtransmission of a portion of the incident light to allow forphotochromic transitioning of the transition material. In someembodiments, the material comprising the substrate, and/or an adhesivefor applying the variable optical filter to a surface, may have UVblocking activity. The UV blocker can be a polymer film comprising anorganic UV absorbing compound (for example xanilides, benzophenones,benzotriazoles hydroxyphenyltriazines or the like), or an inorganic UVabsorbing material (for example nano zinc particles), or a UV reflectingcompound (for example nano-titanium or nano zinc), or a combinationthereof. Examples of UV blocking films, materials or agents that may becombined with a substrate (e.g. when it is mixed, molded, cast orcross-linked), or included in a transition material are provided herein.A UV blocker may be deposited by any suitable method, for examplechemical vapor deposition, physical vapor deposition, (e.g. sputtering,electron beam evaporation, and ion plating), plasma spray techniques,sol-gel processes or the like. In some embodiments, an adhesive employedto affix an optical filter in the form of a film to a pane of a windowor a lens may be, or comprise, a UV blocker. Blocking a portion of theincident UV light may increase the durability of the optical filter.

One skilled in the art will appreciate that the thickness of theselected substrate may be configured so as to allow for sufficientstructural integrity to support the transition material while providingsufficient rigidity or flexibility for the particular application ofuse, as well as sufficient transparency. Determination of an appropriatematerial and thickness is considered to be within the ordinary skills ofa worker in the art. In one embodiment of the invention, the substratehas a thickness of between about 0.012 mm and about 10 mm. The substratemay be rigid or flexible. In one embodiment, the substrate material isrigid and has a thickness of between about 0.5 mm and 10 mm, or betweenabout 1 mm and 5 mm, or a thickness of about 0.5, 1, 2, 3, 4, 5, 6, 7,8, 9 or 10 mm, or any amount or range therebetween. In one embodiment,the substrate material is flexible and has a thickness of between about0.024 mm and about 0.6 mm, or between about 0.051 mm (about 2 mil) toabout 0.178 mm (about 7 mil), or a thickness of about 0.2, 0.3, 0.4,0.5, 0.6, 0.7, 0.8, 0.9 or 1 mm, or any amount or range therebetween.

Combinations of substrate materials and thicknesses are alsocontemplated for use in the variable transmittance optical filter of thepresent invention. In some embodiments, a variable transmittance opticalfilter of the present invention comprises a first layer with a UVblocker material. In some embodiments, a variable transmittance opticalfilter of the present invention comprises a first layer with a substratethat is rigid and a third layer with a substrate that is flexible. In afurther embodiment, a variable transmittance optical filter of thepresent invention comprises a first layer with a substrate having athickness of 5 mil and a third layer having a substrate having athickness of 2 mil.

The substrates can optionally include additives such as base colourtints to provide a darker overall range or colour to the optical filter,and/or UV blocking compounds to block certain wavelengths ofelectromagnetic radiation. In some embodiments, the optical filter ofthe present invention comprises a first layer and/or a third layer witha substrate having a barrier coating to block moisture. In someembodiments, the substrate of the first and/or third layer has ananti-reflective coating. In some embodiments, the substrate of the firstand/or third layer has a scratch resistant coating. In some embodiments,the first and/or third layer has a substrate having a pressure-sensitiveadhesive coating for laminating the variable transmittance opticalfilter onto glass. In some embodiments, an air gap may be providedbetween the third layer and an adjacent layer, for example to facilitatethermal insulation.

1.2. Substantially Co-Planar (SC) Electrode System

The SC electrode system is made of transparent electrically conductivematerial that can be adhered to or etched in a layer on thesubstantially transparent substrate. The SC electrode system comprisesat least one pair of electrically separate electrodes arranged in asubstantially co-planar manner on the substantially transparentsubstrate. A potential difference may be applied across the pair ofelectrodes. For example, each pair of electrodes may comprise oneelectrode to which a positive potential is applied (anode) and oneelectrode to which a negative potential is applied (cathode). In someembodiments, the anode and cathode may be switchably reversed byreversing the polarity on the pair of electrodes so that the anodebecomes the cathode and the cathode becomes the anode.

The SC electrode system may comprise multiple pairs of electrodes thatcan be controlled as a single unit, in groups, or individually in orderto provide fine tuning of the transition of the variable transmittanceoptical filter from one state of visible light transmittance to another.SC electrode systems with multiple electrode pairs may thus be useful inembodiments where the transition from one state of visible lighttransmittance to another in some areas of the variable transmittanceoptical filter is to be controlled differently from that in other areasof the variable transmittance optical filter.

As described herein, in some embodiments, the application of voltage tothe SC electrode pairs can be reversed in polarity one or more times inorder to facilitate transition of the transition material from one stateof visible light transmittance to another.

1.2.1 Transparent Electrically Conductive Material

The variable transmittance optical filter comprises a substantiallyco-planar electrode system having electrodes made of transparentelectrically conductive material that can be adhered in a layer to, orotherwise disposed on, the substrate. This material is typically aninorganic or intrinsically conducting organic material. Suitablematerials for the transparent conductive layers are well-known to thoseskilled in the art and include, for example, metal oxides, carbonnanotubes, and fine wire meshes. Exemplary conductive materials includelayers of doped indium tin oxide, doped tin oxide, doped zinc oxide,antimony tin oxide, polyaniline, graphene, PEDOT(poly(3,4-ethylenedioxythiophene)), PEDOT:PSS(poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)), andpolypyrrole as well as thin, substantially transparent metallic layerssuch as gold, silver, aluminum, and nickel alloy.

In embodiments of the present invention, the electrodes of the SCelectrode system may be formed from a transparent conductive materialgenerally exhibiting a predetermined sheet resistance. As would bereadily understood by a worker skilled in the art, increased sheetresistance in some transparent conducting materials may correspond withincreased VLT. In some embodiments of the invention, the variabletransmittance optical filter of the invention comprises SC electrodesystem formed from a transparent conductive material having a sheetresistance of up to about 100 Ohms/square, or up to about 1000Ohms/square, or up to about 100,000 Ohms/square or up to about 1,000,000Ohms/square, or any amount or range therebetween. In some embodiments ofthe invention, the transparent conductive material may have a sheetresistance from about 10 Ohms/square to about 1000 Ohms/square; or fromabout 20 Ohms/square to about 500 Ohms/square; or from about 100Ohms/square to about 1,000 Ohms/square; or from about 1,000 Ohms/squareto about 10,000 Ohms/square; or from about 10,000 Ohms/square to about1,000,000 Ohms/square; or from about 1,000,000 Ohms/square to about5,000,000 Ohms/square; or from about 5,000,000 to about 10,000,000Ohms/square; or any amount or range therebetween.

As will be understood by one of skill in the art, the first layercomprising a substantially transparent substrate with a transparentelectrically conductive coating, may be selected to have a high degreeof visible light transmittance (VLT), or a low degree of VLT, dependingon the intended use of the optical filter. For example, the firstsubstrate with conductive layer may have a VLT of at least 50%, at least60%, at least 70%, at least 80%, at least 90%, or at least 95%, or anyamount or range therebetween. For an embodiment where the optical filteris desired to block at least 90%, or substantially all light (e.g. anopaque, or substantially opaque optical filter when in a dark state),the first substrate with conductive layer may be selected, or configuredfor a VLT of less than 50%, or less than 40%, or less than 30%, or lessthan 20% or less than 10%, or any amount or range therebetween.

1.2.2 SC Electrode System Pattern

The SC electrode system comprises at least one pair of electricallyseparate electrodes (first and second electrodes) arranged in asubstantially co-planar manner on the substantially transparentsubstrate. A positive and negative potential may be applied to theseelectrodes, or the electrode system, as described herein. As describedherein, it is contemplated that an electrode acting as an anode may beswitched such that it acts as a cathode, by reversing the polarity ofthe voltage applied, and, as described herein, it is contemplated thatan electrode acting as a cathode may be switched such that it acts as aanode, by reversing the polarity of the voltage applied.

In some embodiments, the SC electrode system comprises a plurality (morethan one) pairs of electrodes located in different regions of the firstlayer of the variable transmittance optical filter. This may allowindividual control of different regions of the variable transmittanceoptical filter, as noted above. In some embodiments, the plurality ofpairs of electrodes may include from about 2 to about 10000 pairs ofelectrodes, or more, or any amount or range therebetween, for example,2, 5, 50, 100, 500, 1000, 2000, 5000, 10000 or any amount or rangetherebetween.

In some embodiments, the SC electrode system is designed in aninterdigitated pattern whereby the electrodes of each pair of electrodesare arranged such that the anode and cathode of each pair of electrodesmesh, interlace, alternate, interweave, or are intertwined together, butremain electrically separated. Electrical contact between first andsecond electrodes is provided by the transition material, such as thatdescribed herein. In some embodiments, the SC electrode system isdesigned such that each electrode of the pair of electrodes is proximateto the other over a substantially large portion of the first layer. Insome embodiments where the at least one pair of electrodes is formed inan interdigitated pattern, this may facilitate substantial uniformproximity of the electrodes over a substantial portion of the secondlayer, thereby facilitating substantially uniform transitioning of thetransition material from one state of visible light transmittance toanother.

In some embodiments, the pattern of the electrodes is such that eachelectrode comprises fingers or finger-like structures and the fingers orfinger-like structures of the anode are interdigitated with the fingersor finger-like structures of the cathode. An illustrative example of aninterdigitated electrode pattern is shown in FIGS. 1 and 2. Referring toFIG. 1, an embodiment of a SC electrode system is shown generally at100. The electrode system comprises a first electrode 102 and secondelectrode 104, each comprising a plurality of digits 202 a and 202 b. Inthe embodiment shown, the electrodes each comprise a bus bar portion106, 108. Digit spacing A, digit width B, digit length C and interdigitspacing D are indicated.

FIG. 2 illustrates a cross section along E-E of a variable transmittanceoptical filter comprising the SC electrode system of FIG. 1, showngenerally at 200. The variable transmittance optical filter 200comprises a first substantially transparent substrate 201 having first202 a and second 202 b interdigitated electrodes disposed thereon. Thetransition material 203 of the second layer (schematically illustrated,actual proportion of electrode dimension and/or second layer and/orother elements of the optical may vary) is disposed on the electrodes.In the embodiment illustrated, an optional, substantially transparentsubstrate 204 is included, in contact with the second layer. In someembodiments, seals 205 may be required to keep the transition materialsandwiched between the first and third layers as well as to bond the twosubstantially transparent substrates together. In some embodiments, thetransition material 203, may have adhesive functionality and/or comprisean adhesive component and maintain the bond of the first layer and thirdlayer to the transition material of the second layer; in such anembodiment, seals may not be needed. In some embodiments, spacerelements can be incorporated between the substrates in order to maintaina constant distance between them. The spacer elements can be attached tothe substrate or the spacer elements can be freely distributed in thetransition material.

In other embodiments, the pattern of the electrodes is such that theanode and cathode finger-like structures are aligned to form a linear orcurvilinear unit, which can then be arranged in various ways, such as,for example, in rectangular, square, or triangular patterns, or inwaves, swirls, or in a “jelly roll” pattern. An example of a “jellyroll” type of interdigitated electrode system design is shown in FIG. 3.First electrode 210 and second electrode 212 describe a coiledconfiguration on the first substrate 214. Leads (not shown) may connectcontact points 215 and/or 218 of the first electrode, and/or contactpoints 216, 220 of the second electrode to an electrical system toprovide a voltage to the electrodes. Combinations of both thefinger-like structures and swirl patterns are also contemplated, as areother interdigitated shapes and patterns, exemplified in FIGS. 3-7.

In some embodiments, an electrode may comprise a branched or unbranchedstructure, or a combination thereof. As an example of a branchedstructure, one or more conductive protrusions or fingers may branch offfrom a common bus bar. Branched structures may further comprise pluralhierarchical levels of branching, for example a conductive protrusionmay itself be a bus bar with protrusions extending therefrom, providinga configuration having primary, secondary, etc. bus bars and/or primarysecondary, etc. digits. As an example of an unbranched structure, anelectrode may comprise a straight, meandering, “zig-zag” orspiral-shaped conductor. The longest electrical path in a branchedstructure may generally be shorter than that of a comparable unbranchedstructure, hence end-to end electrical resistances exhibited by abranched structure may be less than in a comparable unbranchedstructure.

Other configurations of electrodes include circumferential layout (e.g.FIG. 9), a serpentine layout or the like, as may be appreciated by thoseskilled in the art.

As described above, in some embodiments of the variable transmittanceoptical filter, the SC electrode system comprises electrodes with one ormore than one “fingers”, or finger-like structures, or from about 1 tothousands of fingers or finger-like structures, or any quantity or rangetherebetween, for example at least 2, 10, 100, 100, 10,000, 100,000, ormore fingers or finger-like structures. Fingers or finger-likestructures may be provided in a single group, in plural groups, and/oron one or more hierarchical levels.

The SC electrode system can also be designed to have multiple levels orhierarchies of interdigitation. FIGS. 5-7 and 9 depict exemplary designsfor the SC electrode system, comprising multiple levels or hierarchiesof interdigitation based on the finger-like structures and swirlpatterns described above. Interdigitation may be multilevel orhierarchical in that an interdigitated electrode feature may itselfcomprise smaller interdigitated features, much like, but not limited to,a finite-level approximation to a fractal geometric structure. Referringto FIG. 5, a multi-level interdigitated SC electrode system is showngenerally at 130. First electrode 132 and second electrode 134 eachcomprise a primary bus bar 142, 144. Extending from each of the primarybus bars of the first and second electrodes are a plurality of secondarybus bars (primary digits) 136, 138, forming a primary level ofinterdigitation. Each of the primary digits has a plurality of secondarydigits 140, 146 extending therefrom, forming a secondary level ofinterdigitation. Leads (not shown) may connect the first and secondelectrodes to an electrical system to provide a voltage to theelectrodes.

Referring to FIG. 6, a multilevel interdigitated SC electrode system(“jelly roll” configuration) is shown generally at 150. First electrode152 and second electrode 154 describe a coiled configuration on a firstsubstrate 156. A plurality of short ‘digits’ 166, 168 on each of thefirst and second electrodes interdigitate in the coiled configuration(“coiled”, “coil together”). Leads (not shown) may connect first andsecond electrodes to an electrical system via contacts 158 and/or 160(for the first electrode) and contacts 162 and/or 164 for the secondelectrode), to provide a voltage to the electrodes. FIG. 7 illustratesgenerally at 170 another embodiment of a multi-level interdigitated SCelectrode system, comprising a plurality of ‘jelly roll’ subunits. First172 and second 174 electrode pairs form an interlocking coiled pattern,providing a greater density of electrodes.

One of skill in the art would understand that other SC electrode systemdesigns with multiple levels of interdigitation are also possible. Suchmultiple levels of interdigitation can be used to cover larger surfaceareas in cases where the surface area that needs to be covered is toolarge for a single interdigitated electrode pattern to cover. The busbars themselves can also form an interdigitated electrode pattern asexemplified in FIG. 5. Additional levels of electrodes can also becreated in the same or similar repeating patterns. In some embodiments,a thinner electrode structure can be used at the lower level of ahierarchical electrode system, and the bus bars can be wider forelectrical conductivity. For example, in some embodiments, the smallestelectrode structures can be 0.015 mm wide, while the bus bars are 0.05mm wide.

One of skill in the art would understand that the specificinterdigitated SC electrode system designs described above are onlyexamples of suitable designs, and that other interdigitated patternscould also be used in the variable transmittance optical filtersaccording to various embodiments. A worker skilled in the art would beable to determine specific interdigitated designs of the SC electrodesystem that are appropriate for certain applications. For example,interdigitated SC electrode systems similar to those exemplified inFIGS. 5 and 7 with multiple levels of interdigitation could be used indevices such as architectural smart windows and automotive smartwindows, where the surface area of the window is larger. In contrast,interdigitated SC electrode systems exemplified in FIGS. 3, 6 and 9could be used for round, oval, or other shaped devices such asophthalmic lenses.

The finger-like structures of the first and second electrodes areseparated by a predetermined separation distance (interdigit spacing Dof FIGS. 1, 4). The predetermined separation distance may be an averagedistance, minimum distance, and/or maximum distance, and may beconfigured, along with other factors of the variable transmittanceoptical filter, in order to effect operation of the optical filter underpredetermined conditions. For example, the separation distance may beconfigured so that application of a predetermined voltage to theelectrodes effects a transition of the optical filter in a predeterminedamount of time. The separation distance D between adjacent structures ofthe first and the second electrodes of the SC electrode system may varydepending on digit spacing (A) and/or digit width (B) or other factors.In some embodiments, D is less than 5 mm, or less than 1 mm, or lessthan 500 μm, or less than 50 μm, or less than 10 μm. In someembodiments, the predetermined separation distance between the anode andthe cathode of the SC electrode system is from about 10 μm to about 5mm, or from about 10 μm to about 100 μm, or from 10 μm to about 1 mm orfrom about 20 μm to about 70 μm, or from about 25 μm to about 50 μm, orany amount or range therebetween.

In embodiments of the present invention, the first and second electrodesare substantially electrically separate, although the distance betweenthem may be small. For example, the transparent substrate upon which theelectrodes are disposed may provide sufficient insulation even at thepoints of closest approach between anode and cathode. Likewise, gapsabove the transparent substrate, in the plane of the electrodes, may beoccupied by sufficiently insulating material, such as that of thetransparent substrate, air, or the like. The distances between first andsecond electrodes, insulating material interposed therebetween, andoperating voltage, may together be configured so as to limit currenttravelling through the insulating material to below a predeterminedlevel, and/or to avoid dielectric breakdown of the insulating material.In an embodiment of the present invention, the sheet conductivity of thematerial (insulating material) between the electrodes is greater thanabout 100 Ohms, or greater than about 1000 Ohms, or greater than about10 kOhms, or greater than about 1 MOhm, or from about 100 Ohms to about1 MOhms or any amount or range therebetween.

In some embodiments, the SC electrode system of the variabletransmittance optical filter comprises electrode structures withsymmetric surface areas and/or widths, asymmetric surface areas and/orwidths, or a combination thereof FIGS. 1 and 4 illustrates dimensionsdigit spacing A, digit width B, digit length C, and separation distanceD, for a system where the first and second electrodes are ofsubstantially the same size and configuration, Dimensions A-D may bedescribed as values (e.g. lengths or width) or as ratios of thedimension. For example, an SC electrode system where the first andsecond electrodes are of substantially equivalent width or area may bedescribed as a width ratio of about 1:1, or as an area ratio of about1:1.

According to some embodiments, digit spacing (A) and/or digit width (B)of each electrode may independently be any suitable dimension from about0.001 mm to about 5 mm, or any amount or range therebetween, for exampleabout 0.01 to about 0.05 mm, or about 0.05 to about 0.1 mm, or about 0.1mm to about 0.5 mm, or about 0.1 to about 1.0 mm. The first and secondelectrodes together may comprise from about 50% to about 99% of thesubstrate upon which they are disposed, or at least about 50%, 60%, 70%,80%, 90% or 95% of the substrate upon which they are disposed. Accordingto some embodiments, electrode features at different levels of ahierarchical electrode structure may have different widths.

In some embodiments, the SC electrode system is designed withsubstantially equal electrode widths, in which the width of the firstelectrode is approximately the same as the width of the second electrode(e.g. B1 is substantially equal to B2). In such embodiments, thepredetermined separation distance is such that the electrodes structuresare spaced closely together and the electrode width is small. The closespacing of the electrodes and the width of the electrodes can facilitatetransitioning of the variable transmittance optical filter from onestate of visible light transmittance to another if the electrodes areclose enough to allow the change in the transition material over oneelectrode to “diffuse” over the nonconductive spaces between theelectrodes.

FIG. 4 illustrates an embodiment where the first and second electrodeshave different size and configuration (first and second electrodes areasymmetric). Referring to FIG. 4, another embodiment of a SC electrodesystem is shown generally at 120. This asymmetric electrode systemcomprises a first electrode 122 and second electrode 124, eachcomprising a plurality of digits. In the embodiment shown, theelectrodes each comprise a bus bar portion 126, 128. Digit spacing (A1and A2), digit width B1 and B2, digit length C and interdigit spacing Dare indicated.

In the embodiment shown in FIG. 4, digit spacing of the first electrode(A1) is less than digit spacing A of the second electrode (A2); digitwidth of the first electrode (B1) is greater than digit width of thesecond electrode (B2). It will be appreciated that the description isalso applicable to an embodiment where A1 is greater than A2 and/or B1is less than B2 In this embodiment, digit length C and interdigitspacing D are substantially the same for both first and secondelectrodes. In an embodiment where one or both electrodes are of acurvilinear, or circumferential or other shaped layout, the relativeareas of the first and second electrodes may be described. Forembodiments where the electrodes are of differing width and/or spacing(asymmetric electrodes), a ratio of B1:B2 or vice versa may be fromabout 2:1 to about 10:1 or about 20:1 or about 30:1 or about 40:1, orabout 50:1, or any amount or range therebetween, for example 2:1,3.33:1, 5:1, 10:1, 20:1, or about 33:1. A ratio of A1:A2 or vice versamay be from about 2:1 to about 10:1 or about 20:1 or about 30:1 or about40:1, or about 50:1, or any amount or range therebetween, for example2:1, 3.33:1, 5:1, 10:1, 20:1, or about 33:1. In some embodiments, anasymmetric SC electrode pattern can provide improved uniformity of VLTover the area of the optical filter while transitioning from one stateof visible light transmittance to another with fewer electrodes, orreduced surface area of electrodes. This may allow for simplification ofmanufacture (e.g. less rigorous etching or printing of narrow or fineelectrodes. In some embodiments, one electrode of each pair ofelectrodes has a larger surface area and/or width than the other. Areaof an electrode may be calculated by, for example, multiplication of thedigit length C by digit width B. Thus, for a system with an asymmetricelectrode configuration, B1×C1 is greater than B2×C2.

For an SC electrode system with asymmetric electrodes, the first andsecond electrodes may have a relative area of about 2:1 to about 1000:1,or any amount or range therebetween, for example about 3:1, about 5:1,about 10:1, about 20:1, about 40:1, about 80:1, about 90:1, about 100:1,about 200:1, about 300:1, about 400:1, about 500:1 about 750:1, or anyamount or range therebetween. The first electrode may comprise fromabout 50 to about 99.9% of the area, or about 50, 55, 60, 65, 70, 75,80, 85, 90, 95 or 99% of the area or any amount or range therebetween.

In some embodiments, the electrodes are configured and shaped so as todrive transitioning of the transition material over substantially theentire area of the optical filter. Interdigitation of electrodes mayallow for a sufficient potential voltage difference to be applied insubstantially all regions of the window to facilitate driving thetransition substantially uniformly over the whole optical filter area.

In some embodiments, the SC electrode system is designed such that itcomprises only two electrodes side by side (i.e. two finger-likestructures of an interdigitated electrode). These electrodes may be thesame width or different widths. If the widths of the electrodes eachhave a width, for example, within 25% of each other (e.g. width ratio ofabout, or less than, 1:1.25), and are in a first range, then an ACmethod of fading, as described elsewhere herein may be used in order tospeed up transition from one state of visible light transmittance toanother. The first range may be: greater than 1 m, greater than 100 mm,greater than 10 mm, greater than 1 mm, greater than 0.5 mm, greater than0.1 mm, or greater than 0.05 mm. If the widths of the electrodes aredifferent, the first electrode can be one or more orders of magnitudelarger than the second electrode.

The first electrode may be an anode and the second electrode a cathode,or vice versa, depending on the polarity of the voltage applied. In oneembodiment, for example, the SC electrode system may have most of itsarea at a positive potential (anode) and just a small area or a smallstrip at a negative potential that serves as the cathode. Such anembodiment may comprise two interdigitated electrodes, or “fingers” withone very wide anode finger and a thin cathode finger.

In some embodiments, the variable transmittance optical filter comprisesan SC electrode system where the anode structures has a larger area thanthe cathode structures (the first electrode is an anode and the secondelectrode is a cathode). This type of electrode design may be used whenthe variable transmittance optical filter comprises a transitionmaterial in which a transition from one state of visible lighttransmittance occurs predominantly at or near the anode. In someembodiments, the variable transmittance optical filter comprises an SCelectrode system where the cathode structures are wider than the anodestructures (the first electrode is a cathode and the second electrode isan anode). This type of electrode design may be used when the variabletransmittance optical filter comprises a transition material in which atransition from one state of visible light transmittance to anotheroccurs predominantly at or near the cathode.

In some embodiments, where the cathode is wider than the anode, both theanode and the cathode are very narrow, and the difference in widthbetween them is small.

In some embodiments, the voltage applied to a symmetric or asymmetric SCelectrode system can be reversed in polarity one or more times in orderto facilitate transition of the transition material from one state ofvisible light transmittance to another. Thus, the invention alsoprovides for a method of transitioning a transition material from afirst state of light transmission to a second state of lighttransmission comprising the steps of applying a positive voltage to afirst electrode and a negative voltage to a second electrode andreversing the polarity of the voltage, thereby applying a negativevoltage to the first electrode and a positive voltage to the secondelectrode. The first state of light transmission may be a dark state,and the second state of light transmission may be a faded, or lightstate.

The voltage can applied to the variable transmittance optical filter byconnecting the source of electric voltage to the at least one pair ofelectrodes of the SC electrode system and the polarity of the voltagecan be switched back and forth between the electrodes in each pair(essentially switching the anode and cathode back and forth between thetwo electrodes). This switching of polarity may allow for more rapid andeven transition over the full area of the optical filter from one stateof visible light transmittance to another. In some embodiments, wherethe variable transmittance optical filter comprises a transitionmaterial that is a hybrid P/E switching material, reversing the polarityof voltage applied to the electrodes of the SC electrode system resultsin completion of the transition from dark to light states.

Switching the polarity of the voltage can be done at fairly lowfrequency, for example, only once during the transition from one stateof visible light transmittance to another or by applying an AC signal(AC power) to the variable transmittance optical filter, or by reversinga DC signal. In some embodiments, the switching frequency is the sameorder of magnitude as the reciprocal of the transition time of theoptical filter. Alternatively, higher switching frequencies can be used.It will be readily understood that switching frequencies may be limitedby capacitive effects induced by the electrode structure. This methodallows wider and hence less expensive patterns of interdigitatedelectrodes to be used while still allowing full transition from onestate of visible light transmittance to another over the interdigitatedelectrode area. Thus, in some embodiments, the variable transmittanceoptical filter comprises an SC electrode system in which the polarity ofvoltage is switched at a frequency of less than 2 kHz, or less than 1kHz, or less than 0.5 kHz, or less than 0.1 kHz. In some embodiments,the variable transmittance optical filter comprises an SC electrodesystem in which the polarity of the voltage is switched at a frequencyranging from about 0.1 kHz to about 2 kHz, or any amount or rangetherebetween. In some embodiments, the variable transmittance opticalfilter comprises an SC electrode system in which the polarity of voltageis switched by the application of a square wave applied in a frequencyof up to about 1 kHz.

In some embodiments, the polarity can be switched periodically orquasiperiodically to produce an applied voltage generally characterizedby a square wave with a predetermined maximum voltage, minimum voltage,duty cycle, and average. In one embodiment, maximum and minimum voltagelevels obtained by the square wave include −2 V and +2 V and/or 1 V and3 V, and/or 0.5 V and 5 V, and/or 0.1 V and 10 V, and/or 0.001 V and 140V; or any amount or range therebetween. It would be readily understoodthat other voltage levels may be suitable.

1.2.3 Preparation of SC Electrode System

The SC electrode system can be prepared according to methods known inthe art. Typically, the transparent conductive material is disposed onthe substantially transparent substrate of the first layer of thevariable transmittance optical filter. The desired pattern of electrodesmay be etched into the electrically conductive material by processesknown in the art, such as additive photolithography, subtractivephotolithography, silk screening, milling, engraving, vapour deposition,electroplating and wet (for example, HCl) or dry (for example, CH₄, O₂,HBr, Cl₂, and the like) etching techniques. As is known in the art,pulsed laser techniques can also be used to pattern the electricallyconductive material. Additive processes such as drop on demand printingor masking and then depositing material in the non-masked areas to formthe electrodes are also suitable for preparing the SC electrode systemaccording to the present invention. In embodiments where the SCelectrode system is designed with asymmetric electrode widths, thenumber of very thin electrodes that need to be etched may be reduced. Assuch, in some embodiments, variable transmittance optical filters havingan SC electrode system with asymmetric electrode widths may be lessexpensive to manufacture.

The etching processes described above use a substrate with a conductivecoating as the starting point. Methods of applying the electricallyconductive material to the substrate to form suitable conductive layersare well known in the art. For example, substrate materials pre-coatedwith indium tin oxide (ITO) are available from a number of suppliers,including CP Films of St. Louis, Mo. and Southwall Technologies Inc. ofPalo Alto, Calif. (now Solutia Inc. St. Louis Mich.). One skilled in theart will recognize that multiple layers of conductive materials can alsobe employed in the optical filter of the present invention.

The conductive layers are disposed on the substrate as a coating. Theconductive layer is coated or deposited onto the substrate to athickness that provides adequate conductance for the optical filter, andwhich does not appreciably interfere with the required transmission oflight. In one embodiment, the thickness of the conductive layer rangesfrom about 1 nanometer to about 90 microns. In another embodiment, thethickness of the conductive layer ranges from about 10 nanometers toabout 10 microns.

2. Second Layer Comprising a Transition Material

As indicated above, the variable transmittance optical filter with an SCelectrode system comprises a second layer proximate to the first layer,the second layer comprising a transition material capable of dynamicallyvarying the degree of visible light transmittance. The transitionmaterial can be a material or system known in the art. Exemplary,non-limiting transition materials include those used in electrochromic,liquid crystal, and suspended particle technologies. In someembodiments, the transition material can be a hybridphotochromic/electrochromic switching material, and may comprise ahybrid photochromic/electrochromic compoundas exemplified herein.

The state of visible light transmittance can include a dark state, alight state, an opaque state, or a clear state. For example, manyelectrochromic technologies result in a change from a dark state to alight state, or vice-versa. Liquid crystal technologies typically resultin a change between a clear state and a translucent or opaque state.Suspended particle technologies result in a change from a light state toa dark state.

In embodiments where there is no optional third layer, and thus only onesubstantially transparent substrate, the transition material is disposedon the surface of the substantially transparent substrate, and incontact with the SC electrode system. In other embodiments where thevariable transmittance optical filter comprises a third layer that is asubstantially transparent substrate, the transition material is disposedbetween the first layer and the third layer and in contact with the SCelectrode system.

2.1 Hybrid PhotochromidElectrochromic Switching Material

In one embodiment, the variable transmittance optical filter of theinvention comprises a transition material that is a hybridphotochromic/electrochromic (“hybrid P/E”) switching material. A hybridP/E switching material has both electrochromic and photochromicproperties. A hybrid P/E switching material may darken (e.g. reach a‘dark state’) when exposed to light from a light source, and may lighten(“fade”, “electrofade”, “bleach”, “electrobleach”, achieve a ‘lightstate”) when exposed to an electric charge. Such a switching materialmay be alternately described as an auto-darkening material. In someembodiments, the switching material may fade upon exposure to selectedwavelengths of visible (VIS) light, without sacrifice of the ability tobe electrofaded when restored to a darkened state.

In some embodiments, the hybrid P/E switching material is a liquid, asolid, a sol-gel or a gel. The liquid, sol-gel or gel may be of a rangeof viscosity.

The thickness of the layer of hybrid P/E switching material may affectthe transmittance of the variable transmittance optical filter of theinvention and may be selected depending on the particular applicationdesired. For example, when comparing a thinner and a thicker layer ofhybrid P/E switching material comprising the same concentration of dye,the thicker layer will provide a lower percentage visible lighttransmission in the dark state. In some embodiments of the invention,the hybrid P/E switching material has a thickness from about 0.1 micronsto about 10,000 microns; or from about 1 to about 1000 microns; or fromabout 10 microns to 100 microns, or any amount or range therebetween.Typically, uniform thickness of the hybrid P/E switching material willbe desired in most applications; however, it is contemplated that avariable transmittance optical filter of the invention can comprise anon-uniform thickness of the hybrid P/E switching material forapplications where some darker regions and some lighter regions aredesired.

The hybrid P/E switching material comprises a hybrid P/E compound(“hybrid dye”, “hybrid chromophore”)) that has a dark state and a lightstate. In certain embodiments, the hybrid P/E switching material, maycomprise one or more optional components. For example, the hybrid P/Eswitching material may further comprise one or more of a solvent, anelectrolyte, a polymer, a charge compensator, a charge carrier, a UVstabilizing agent, a UV blocking agent, a tinting agent, or the like.One skilled in the art will recognize that certain components may beable to fill dual roles in the hybrid P/E switching material, forexample, certain dyes may self-polymerize and fulfill the role of bothdye and polymer; certain polymers may also have UV blockingcapabilities; or the like. Conversely, in some embodiments, a givencomponent may be made up of several individual compounds, e.g., thepolymer component may be a copolymer comprising different monomericunits.

In one embodiment, the hybrid P/E switching material of the inventioncomprises a chromophore and a component in which the chromophore issoluble such as a solvent or a polymer, or a polymer that fulfills thefunction of a solvent. In another embodiment, the hybrid P/E switchingmaterial of the invention comprises a chromophore, a solvent, and atleast one optional component selected from the group consisting of: a)an electrolyte; b) a polymer component; c) a charge compensator; d) acharge carrier; e) a UV stabilizing agent; f) a UV blocking agent; andg) a tinting agent.

Hybrid P/E Compounds:

The hybrid P/E switching material according to the present inventioncomprises one or more organic compounds (“dyes” or “chromophores”) thatexhibit both photochromic and electrochromic characteristics. These dualmode compounds are capable of reversibly switching between two distinctisoforms when stimulated electrically and by light. The hybridphotochromic/electrochromic compounds that can be used in the presentinvention are organic, and include classes of compounds from thehexatriene family, for example, the class of compounds known in the artas diarylethenes, dithienylcyclopentenes, and fulgides. In someembodiments, switching of the compound to the ring-open form is inducedby application of a voltage to a switching material comprising thecompound, and is independent of the polarity of the applied voltage. Thehybrid P/E compound may be an anodic species, that is, theelectrochromic colour change (electrochromic fading, electrochromictransition from a dark state to a light state) occurs primarily at theanode. The hybrid P/E compound may from a faded state to a dark statewhen exposed to light of a wavelength comprising a portion of the UVrange, for example from about 300 to about 450 nm, or any amount orrange therebetween, for example from about 350 to about 420 nm, or fromabout 365 to about 420 nm, or from about 375 to about 420 nm, or fromabout 375 to about 420 nm, or from about 380 to about 420 nm, or fromabout 385 nm to about 420 nm, or any amount or range therebetween.

According to one embodiment of the invention, the hybrid P/E switchingmaterial comprises one or more chromophores from the class of compoundsknown as diarylethenes. Examples of diarylethenes include derivatives of1,2-dithienylcyclopentene as described in International PatentPublication No. WO 2004/1015024, having the general structure of Formula1 below:

wherein each R₁ is independently H or a halogen;

Z is N, O or S;

wherein each R₂ is independently H, a halogen, or both R₂ when takentogether form CH═CH, or when in polymeric form R₂ is CH═CH and formspart of a polymer backbone;wherein each R₃ is independently alkyl, aryl, H, a halogen or CO₂Y (Y═H,Na, alkyl, aryl); wherein R₄ is aryl; andwherein each R₅ is independently H, alkyl or aryl.

“Aryl” includes substituted or unsubstituted benzyl or thiophenyl.Substitutions may be alkyl, halogen or the like. Benzyl may besubstituted in ortho-, meta- or para-positions of the benzyl ring.Thiophenyl may be substituted at one or more of positions 2, 3, 4 or 5of the thiophene ring.

“Halogen” includes F, Br and Cl.

“Alkyl” includes methyl, ethyl, propyl, butyl, t-butyl.

Preparation of exemplary fluorinated dithienylcyclopentene derivativesthat may be incorporated in the switching materials of the inventionfollows the general methodology of Scheme 1 below:

In one embodiment of the invention, the switching material comprisescompounds of Formula 1 wherein R₁ and R₂ are F, R₃ and R₄ are

(X═S), and R₅ is H. In another embodiment of the invention, theswitching material comprises compounds of Formula 1 wherein R₁ and R₂are F, R₃ is H, R₄ is

(X═S), and R₅ is H.

In a further embodiment of the invention, the switching materialcomprises compounds of Formula 1 wherein R₁ and R₂ are F, R₃ and R₄ areindependently

or and, and R₅ is H. In another embodiment of the invention, theswitching material comprises compounds of Formula 1 wherein R₁ and R₂are F, R₃ is H, R₄ is

and R₅ is H. In a further embodiment of the invention, the switchingmaterial comprises compounds of Formula 1 wherein R₁ and R₂ are F, R₃ is

(X═S), R₄ is CH₃, and R₅ is H. In another embodiment of the invention,the switching material comprises compounds of Formula 1 wherein R₁ andR₂ are F, R₃ is

(X═S); R₄ is CH₃, and R₅ is H.

The chromophores can be incorporated into the switching material inmonomeric or polymeric forms depending on the functional demandsrequired. The compounds of Formula 1 may be incorporated in polymericform as part of the polymer backbone or as a pendant group. For example,fluorinated compounds may be polymerized using ring-opening metathesispolymerization in accordance with Scheme 2 below:

Exemplary non-fluorinated dithienylalkene derivatives that may beincorporated in the switching materials of the invention can be preparedin accordance with the general methodology of Scheme 3 below:

In one embodiment of the invention, the switching material comprises acompound of Formula 1 wherein R₁ is H, R₂ is CH═CH, R₃ is C₁, R₄ is CH₃,and R₅ is H. In another embodiment of the invention, the switchingmaterial comprises a compound of Formula 1 wherein R₁ is H, R₂ is CH═CH,R₃ is CO₂CH₃, R₄ is CH₃, and R₅ is H. In a further embodiment of theinvention, the switching material comprises a compound of Formula 1wherein R₁ is H, R₂ is CH═CH, R₃ is

(X═S), R₄ is CH₃, and R₅ is H.

In other embodiments of the invention, the switching material comprisesa compound of Formula 1 wherein the compound forms part of a polymer. Inone embodiment of the invention, R₁ is H, R₂ is CH═CH and forms part ofthe polymer backbone, R₃ is C₁, R₄ is CH₃, and R₅ is H. In a furtherembodiment of the invention, the switching material comprises a compoundof Formula 1 wherein R₁ is H, R₂ is CH═CH and forms part of the polymerbackbone, R₃ is CO₂CH₃, R₄ is CH₃, and R₅ is H. In another embodiment ofthe invention, the switching material comprises a compound of Formula 1wherein R₁ is H, R₂ is CH═CH and forms part of the polymer backbone, R₃is CO₂H, R₄ is CH₃, and R₅ is H. In another embodiment of the invention,the switching material comprises a compound of Formula 1 wherein R₁ isH, R₂ is CH═CH and forms part of the polymer backbone, R₃ is

(X═S), R₄ is CH₃, and R₅ is H.

An example of a suitable chromophore for inclusion in the hybrid P/Eswitching material is one that exhibits both photostability as well aselectrochemical durability. The photostability of a compound, e.g., theresistance of the chromophore to light induced degradation, can bemeasured by the amount of time it takes for the compound to degrade to acertain point under constant light exposure. For example, in oneembodiment the compound can be measured in its dark state and its lightstate to determine its contrast ratio prior to testing. During testing,the contrast ratio is monitored periodically to determine degradation.Failure can be determined to occur when the contrast ratio falls below acertain level, or when the contrast ratio falls below 50% of theoriginal contrast ratio. Other methods for testing are within theknowledge of persons skilled in the art. The photostability ofembodiments of the invention can be tested using a Xenon-arc lamp, forexample in a Q-Sun testing unit made by Q-Lab of Cleveland, Ohio. In oneembodiment, the hybrid P/E switching material of the invention comprisesa chromophore having a photostability in the range of about 1000 hoursto about 5000 hours, or over 5,000 hours of constant light exposure. Theelectrochemical durability of a suitable chromophore is measured as thenumber of cycles that the chromophore can maintain its switchingactivity between the light and dark state. In one embodiment, the hybridP/E switching material of the invention comprises a chromophore havingan electrochemical durability in the range of about 1000 to about 5,000cycles or over 5,000 cycles. Typically, the hybrid P/E switchingmaterial according to the present invention contains (by weight) 0.05%to about 30%, or any amount or range therebetween, for example about 1,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28 or 29%.

Examples of selected hybrid P/E compounds include: S001, S002, S042,S054 and S068; or derivatives thereof having different functional groupsof the peripheral benzyl or thiophene rings.

Solvent:

The solvent component of the hybrid P/E switching material dissolves,intersperses and/or diffuses the one or more chromophores and othercomponents throughout the hybrid P/E switching material. The solventused in the preparation of the switching material is typically inert,i.e., photochemically and electrochemically inactive, and colourless,and has a sufficiently high boiling point to prevent solvent loss undertypical operating conditions. Examples of suitable solvents include, butare not limited to, triglyme, dichloroethane, tetraglyme, propylenecarbonate, ethylene carbonate, water, butyrolactone, cyclopentanone andmixtures thereof. In one embodiment of the present invention, thesolvent component comprises triglyme.

One or more solvents may be present in a switching material in an amountfrom about 50% to about 95% (by weight), or any amount or rangetherebetween, for example 50, 60, 70, 80 or 90%, or any amount or rangetherebetween.

Electrolyte:

Electrolytes are generally electrically conductive, and may includealkali metal salts, tetralkylammonium salts or the like. Examples ofelectrolytes include TBABF₄ (tetrabutylammonium tetrafluoroborate),TBAPF₆ (tetrabutylammonium hexafluorophosphate), tetrabutylammoniumperchlorate, lithium bis(trifluoromethane sulfonimide), lithiumtriflate, LiBOB (lithium bis(oxatlato)borate), LiClO₄ (lithiumperchlorate) or the like. The one or more electrolytes may be present inan amount from about 0.1% to about 10% (by weight) or any amount orrange therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or 9%. Where thesolvent is an ionic solvent, an electrolyte component may be optional.

Polymer Component:

In some embodiments of the invention, one or more polymers or sol-gelsmay be included in the compositions. Examples of polymers includepolyvinylbutyral (PVB) B-90, PVB-B72, poly(methyl methacrylate) (PMMA),nitrile rubber (NBR), polyvinylpyrrolidone (PVP), polyvinylidenefluoride (PVDF), poly(dimethylsiloxane) (PDMS), poly(ethyl methacrylate)(PEMA), The one or more polymers or sol-gels may be present in an amountfrom about 0.1% to about 30% (by weight) or any amount or rangetherebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18,20, 22, 24, 26, 28 or 30%, or any amount or range therebetween. In someembodiments the one or more polymers or sol-gels may function as arheology modifier.

Charge Compensator:

In some embodiments of the invention, a charge compensator(charge-transfer complex or charge-transfer salt) may be included in oneor more compositions. A charge compensator may be a cathodic material toaid in redox balance of an anodic chromophore. The charge compensatormay be stable, or sufficiently stable in both reduced and oxidizedforms. The charge compensator may be an organic semiconductor. Examplesof charge compensators include Prussian Blue (PB), ferroceniumtetrafluoroborate, ferrocenium hexafluorophosphate,tetracyanoquinodimethane, tetrafluoro-tetracyanoquinodimethane,1,4-dicyanobenzene, 1,2,4,5-tetracyanobenaene, pyrene, tetracene,pentacene or the like. The one or more charge compensators may bepresent in an amount from about 0.1% to about 10% (by weight) or anyamount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or 9%

Charge Carrier:

The primary role of the charge carrier component is to facilitatetransport of the electrons and “holes” between the two electrodes andconsists of, or any combination of, substances known in the art to besuitable charge carrier materials. The charge carrier used in thepreparation of the hybrid P/E switching material is typically redoxactive in the electrochemical potential range required to trigger colourlightening of the hybrid P/E switching material. Examples of suitablecharge carriers include, but are not limited to tris(4-bromophenyl)amine, tris(4-chlorophenyl) amine, 10-methylphenothiazine,9,9-(N,N,N′,N′-tetrabiphenyl-N,N′-diphenyl)fluorene,4,4′-di(N-carbozolyl)biphenyl, 1-(N-carbozolyl)-4-diphenylaminobenzene,N,N,N′N′-tetraphenylbenzidine, and1-(N-Carbozolyl-4-N′-alpha-naphthyl-N′-phenylamine. The hybrid P/Eswitching material according to the present invention typically containsabout 0.1% to about 10% by weight of the charge carrier component

UV Stabilizer:

The primary role of the UV stabilizer is to inhibit photodegradation ofthe hybrid P/E switching material by scavenging radical intermediatesformed in photodecomposition processes and consists of, or anycombination of, substances known in the art to be suitable UVstabilizing materials. Examples of suitable UV stabilizers include, butare not limited to the class of compounds known in the art as hinderedamine light stabilizers (HALS). One or more UV stabilizers may bepresent in an amount from about 0.01% to about 10% (by weight) or anyamount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or10%.

UV Blocker:

The primary role of the UV blocker (or UV absorber) is to preventphotodegradation of the auto-darkening material by including a componentof the material that absorbs higher energy UV light and dissipates theenergy thermally preventing photodecomposition and consists of, or anycombination of, substances known in the art to be suitable UV blockingmaterials. Examples of suitable UV blockers include, but are not limitedto benzotriazoles, benzophenones. One or more UV absorbers may bepresent in an amount from about 0.01% to about 10% (by weight) or anyamount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or 9%.

Tinting Agent:

Inclusion of a colourant or tinting agent in a composition according tovarious embodiments of the invention may achieve a desired colour and/oradjust the visible light transmission of the composition. A variety ofcolourants are known in the art, and selection of a colourant to achievea desired colour, hue or transmissibility is within the ability of askilled worker. Examples of colourants include one or more chromophoresas described herein, Prussian blue, or the like. One or more colourantsmay be present in an amount from about 0.01% to about 10% (by weight) orany amount or range therebetween, for example 1, 2, 3, 4, 5, 6, 7, 8, or9%

Although the optional components noted above have been described withreference to the hybrid P/E switching material as transition material,one of skill in the art would understand that some of these optionalcomponents could also be used when the variable transmittance opticalfilter comprises a transition material other than a hybrid P/E switchingmaterial.

2.2 Electrochromic Transition Materials

In one embodiment, the variable transmittance optical filter comprisesan electrochromic transition material. Several technologies are wellknown in the art with respect to the design of electrochromic transitionmaterials. Electrochromic transition materials generally comprise threecentral components: an ion storage component, ion conducting componentand electrochromic component. Electrochromic transition materialstypically function as the result of transport of charged ions from theion storage component, through the ion conducting component into theelectrochromic component by applying a voltage. The presence of the ionsin the electrochromic component changes its optical properties, causingit to absorb visible light, the result of which is to darken the window.To reverse the process, the voltage is reversed, driving the ions in theopposite direction, out of the electrochromic component, through the ionconducting component, and back into the ion storage component. As theions migrate out of the electrochromic component, it brightens (or“bleaches”), and the window becomes transparent again.

Several electrochromic components are known in the art and commerciallyavailable and include the organic electrochromic components PEDOT(poly(3,4-ethylenedioxythiophene)), PEDOT:PSS(poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)), polyaniline,polypyrrole, viologen or mixtures thereof. Nonlimiting examples ofsuitable inorganic electrochromic components include WO₃, NiO and IrO₂.These electrochromic components are suitable for inclusion in theelectrochromic transition material of the variable transmittance opticalfilter. Thus in some embodiments the variable transmittance opticalfilter comprises a transition material having an inorganicelectrochromic component. In other embodiments, the variabletransmittance optical filter comprises a transition material having anorganic electrochromic component.

The ion storage component of the electrochromic transition material canbe one of many known in the art. Several non-limiting examples ofsuitable ion storage components include: nickel oxide (NiO), vanadiumoxide (V₂O₅) or iridium oxide (IrO₂).

The ion conducting component of the electrochromic transition materialcan be one of many known in the art. The ion conducting componentcomprises an electrolyte, and can be a solid state or a liquid/polymergel type component depending on the type of electrolyte used. For liquidtype layers, an electrolyte is typically dissolved in a liquid solvent,for example, water or organic solvents (e.g. propylene carbonate,dimethylsulfite, nitromethane, etc.). For polymer gel type layers, anelectrolyte is typically dispersed in a gel-forming polymeric matrix.

Suitable electrolytes that may be used include, for example,lithium-containing electrolytes or proton-based electrolytes. Withproton-based electrolytes the coloring/bleaching processes of theelectrochromic device are much faster since the ionic diffusivity ofprotons is about two orders of magnitude higher than that of lithiumions, thereby making. Lithium-containing electrolytes include, forexample, LiClO₄/propylene carbonate liquid electrolyte, a polymergel-type electrolyte comprising LiClO₄ with gamma-butyrolactone (GBL)and crosslinked methacrylated polyethylene oxide, oxymethylenelinkedpolyethylene glycol or amorphous polyethylene oxide with lithiumtrifluoromethylsulfonyl imide (LiTFSI), LiAlF₄, LiNbO₃, and the like.Proton-based electrolytes include, for example, Nafion™ (C₇HF₁₃O₅S.C₂F₄,polyacrylamido-methyl-propane sulfonic acid (poly-AMPS), polystyrenesulfonic acid (poly-SSA), polyethylene sulfonic acid (poly-ESA),Ta₂O₅.pH₂O, SiO₂.pH₂O, phosphotungstic acid (PWA), zirconium phosphate(ZP) and Sn(NaH)(PO₄)₂.pH₂O.

Additional protective components may be utilized in the electrochromictransition material to improve durability of the variable transmittanceoptical filter. For example, inorganic films, such as Ta₂O₅, Sh₂O₅, ornonporous polymer films, such as ultraviolet light-cured plasticizedpoly (vinyl alcohol), may be used to coat the electrochromic componentto further protect the electrochromic layer from degradation due tocontact with the ion conducting layer.

Methods of depositing electrochromic transition material on thesubstantially transparent substrate are known in the art, for example,sputtering, chemical vapour deposition or the like.

2.3 Other Transition Materials

Other transition materials such as, for example, liquid crystalmaterials and suspended particle materials are known in the art, and maybe suitable for use in the variable transmittance optical filtersaccording to the present invention. One of skill in the art would beable to select additional suitable transition materials capable oftransitioning from one state of visible light transmittance to anotherthat would be suitable for use with the SC electrode system of thevariable transmittance optical filters of the invention.

The thickness of the optical filter according to various embodiments ofthe present invention may vary depending on the thickness and nature ofthe transition material, substrate, conductive layer and any otheroptional layers or components (optional 3rd layer, films or the like).Thinner optical filters may provide greater flexibility and/or fasterfade times, while thicker optical filters may offer darker colour and/orgreater rigidity. In accordance with one embodiment, the thickness ofthe optical filter is from about 10 to about 1000 microns, or from about25 microns to about 250 microns, or from about 25 to about 125 microns,or any amount or range therebetween.

3. Control Circuit

To be operated, the variable transmittance optical filter of the presentinvention is connected to a power source capable of establishing apotential difference (voltage) between the electrodes of the SCelectrode system of the variable transmittance optical filter. In someembodiments, the SC electrode system further comprises one or more busbars to carry current from a power source to the electrodes. A controlcircuit can be used to switch the electrical voltage on or off based oninput from an automated or semi-automated device (e.g. an irradiancemeter, thermometer), a building environmental control system, a user orsome other input, and can also be used to modulate the voltage to apredetermined level. The power for turning the variable transmittanceoptical filter on or off can come from a variety of sources, includingan AC line voltage in a house or other building, a DC power source (e.g.a battery), an energy harvesting power source or the like. Examples ofenergy harvesting power sources include photovoltaic devices (e.g. solarcells, solar panels, or arrays thereof, photoelectric cells or arraysand the like); vibrational-energy harvesting technologies such aspiezoelectrics; mechanical energy converters such as acousticconverters; thermal energy-harvesting devices such as pyroelectric orthermoelectric devices; or the like. The power source is connected tothe variable transmittance optical filter through the control circuit.The control circuit may comprise a switch, such as a transistor, relay,or electromechanical switch that opens and closes the circuit betweenthe power source and the interdigitated electrodes in the variabletransmittance optical filter. The control circuit can also include anAC-DC and/or DC-DC converter for converting the voltage from the powersource to an appropriate voltage to cause a change in the visible lighttransmittance of the variable transmittance optical filter. The controlcircuit may comprise a DC-DC regulator for regulation of the voltage.The control circuit can also comprise a timer and/or other circuitryelements for applying electric voltage to the variable transmittanceoptical filter for a fixed period of time following the receipt ofinput.

Depending on the transition material used in the variable transmittanceoptical filter, the application of voltage to the transition materialwill cause the transition material to either lighten or darken (e.g. ifthe transition material is an electrochromic transition material), or tolighten if the transition material is a hybrid P/E switching material.

Referring to FIG. 8, a control circuit shown generally at 700 may beused to apply a voltage to the interdigitated electrodes of the variabletransmittance optical filter. A power source 720 supplies electric powerto the circuit. In one embodiment, the power source 720 is an AC linevoltage typically found in a home or commercial building. Optional ACtransformer 710 can be used to transform the AC voltage into a DCvoltage for use in the control circuit. Control electronics 740comprising a switch 730 can be used to connect and disconnect the DCvoltage from the variable transmittance optical filter 750. Inembodiments where the power source provides DC current, an ACtransformer may not be required. A power source may be a a building orvehicle electrical system, a battery, or an energy harvesting device,such as a photovoltaic power source.

Embodiments of the invention include switches that can be activatedmanually or automatically in response to predetermined conditions. Forexample, control electronics may process information such as time ofday, ambient light levels detected using a light sensor, user input,stored user preferences, occupancy levels detected using a motionsensor, or the like, or a combination thereof, the control electronicsconfigured to activate switches for applying voltage to the electrodesin response to the processed information in accordance withpredetermined rules or conditions. In one embodiment, the power controlelectronics comprises a user-activated switch that passes the DC voltagefrom the power source substantially directly to the variabletransmittance optical filter. The user activated switch can be anormally-open push button, or another type of switch. A switch may beconfigured to remain closed for a predetermined amount of time followingactuation, thereby facilitating application of voltage to the opticalfilter for sufficient time to effect a state transition.

In some embodiments, a generated DC voltage, for example via an AC-DCtransformer or converter, and/or a DC-DC converter or regulator, ismatched to the voltage required by the variable transmittance opticalfilter in order to trigger a transition from one state of visible lighttransmittance to another. The voltage that can be applied in order forthe variable transmittance optical filter to transition from one stateof visible light transmittance to another will depend on factors such asthe transition material and the resistivity of the electrodes of the SCelectrode system. The voltage may be fixed or it may be controllable bythe control system. In some embodiments where the transition material isa hybrid P/E switching material, the voltage applied ranges from betweenabout 1 to about 12 volts DC. In another embodiments where thetransition material is a hybrid P/E switching material, the voltageapplied ranges from about 0.1 to about 42 volts DC. In other embodimentswhere the transition material is a hybrid P/E switching material, theoptical filter of the invention lightens with the application of lessthan about 12 V, or less than about 6V or less than about 3 V, or lessthan about 2 V, or any amount or range therebetween, In some embodimentsthe amount of voltage applied to electrofade the switching material isfrom about 0.5 to about 3 V, or from about 1.2 to about 2.5 V or fromabout 1.8 to 2.1 V. In some embodiments of the invention, a minimumvoltage is approximately 1.8 volts.

In some embodiments wherein the transition material is an electrochromicmaterial, the variable transmittance optical filter will transition fromone state of visible light transmittance to another with the applicationof a DC voltage in the range of about 3 V to about 5 V. In someembodiments where the transition material is a liquid crystal orsuspended particle material, the variable transmittance optical filterwill transition from one state of visible light transmittance toanother, at higher DC or AC voltages, such as for example, 120 V AC.

In one embodiment of the invention, power control electronics 740 can beused to control the voltage being applied to the variable transmittanceoptical filter 750 of the present invention as well as for controllingthe duration that the voltage is applied. In one embodiment, controlelectronics may include a DC-DC converter for converting and/orregulating the voltage from AC transformer 710. For example, ACtransformer 710 may output a 12 Volt DC voltage. A DC-DC converter canbe used to step the 12 Volt DC voltage down to a lower voltage. In oneembodiment, the variable transmittance optical filter of the presentinvention uses a voltage in the range of 1.2 Volts to 2.1 Volts totransition from one state of visible light transmittance to another.

In another embodiment, the power control electronics 740 controls switch730. In this embodiment, the power control electronics 740 close switch730 in response to user input or input from an electronic device such asa sensor. The user presses a button connected to a normally openmomentary switch to provide an input signal to power control electronics740. The power control electronics 740 then closes switch 730 for afixed period of time. The fixed period of time can be preset and builtinto the power control electronics by using a standard timing circuitfamiliar to those skilled in the art of electronic circuits. The fixedperiod of time would be preset to be the amount of time required for thevariable transmittance optical filter 750 to transition from one stateof visible light transmittance to another.

In some embodiments, a light sensor can also be incorporated into powercontrol electronics 740 to sense when it is bright outside. For example,in embodiments including a light sensor, where a hybrid P/E transitionmaterial is used in the variable transmittance optical filter, if it isbright outside and the user presses the button, the power controlelectronics can maintain a voltage on the variable transmittance opticalfilter 750 in order to maintain the lightened state. Maintaining avoltage on variable transmittance optical filter 750 can serve toover-ride the auto-darkening aspect of the variable transmittanceoptical filter (e.g. when exposed to some wavelengths of light) and keepit in a light state even when it is exposed to UV light. In suchembodiments, the user returns the variable transmittance optical filterto its normal auto-darkening state by pressing the button again, or bypressing a second button.

In some embodiments, for example where the transition material of thevariable transmittance is a hybrid P/E switching material, the powercontrol electronics may be configured to switch the polarity of thevoltage applied to the variable transmittance optical filter one or moretimes, or to otherwise vary the applied voltage. In some embodiments,the voltage polarity may be switched between a positive and a negativepolarity using a double pole double throw switch, or a collection oftransistors, relays, or other electrical or electromechanical switchesconfigured to switchably provide a first circuit path and a secondcircuit path. The first circuit path connects the electrodes to the DCpower source such that a voltage measured from first electrode to secondelectrode is positive, while the second circuit path connects theelectrodes to the DC power source such that a voltage measured fromfirst electrode to second electrode is negative. Such polarity switchingcircuitry would be readily understood by a worker skilled in the art.

In further embodiments, switch 730 is a multi-state control device suchas a potentiostat or a multi-position switch that allows the user toselect various different states of visible light transmittance for thevariable transmittance optical filter 750. For example, the user couldselect an intermediate state to indicate that a state part way betweenfully dark and fully light is desired. Power control electronics 740 canthen apply the voltage to the variable transmittance optical filter 750for a sufficient duration to achieve this intermediate state. A timercircuit or waveform generator or other electronics may be used forapplication of voltage for a controllable period of time, as would bereadily understood by a worker skilled in the art. Other methods ofcausing the variable transmittance optical filters of the invention toreach an intermediate state, such as applying a reduced amount ofvoltage, may also be possible.

In some embodiments, power control electronics 740 can also include avoltage or current sensor, or an optical sensor, that can sense when thetransition from one state of visible light transmittance to another iscompleted in the variable transmittance optical filter 750. For example,when the variable transmittance optical filter with an SC electrodesystem comprises a hybrid P/E switching material, when power controlelectronics 740 sense that the transition process is completed, it willopen switch 730 in order to conserve power. Other functions and featuresthat can be built into power control electronics 740 are alsocontemplated.

Control electronics 740 can also include electronic circuitry to applyan alternating waveform to the variable transmittance optical filter 750instead of a constant DC voltage. The waveform can be in the form of asquare wave, a sawtooth wave, a sinusoidal wave, or some other waveform.The amplitude of the wave may vary. An alternating waveform may beadvantageous for some embodiments, by enabling a faster switching timeand/or a longer product lifetime. In some embodiments, the potentialdifference applied between the two electrodes may be described as asquare wave alternating between a first voltage and a second voltage,each of the first and second voltages being predetermined positive,negative, or zero with respect to ground. A square wave may beimplemented by periodically switching the polarity of the voltageapplied to the electrodes, for example. In one embodiment, a waveformcan be applied to the interdigitated electrodes of the optical filter750 by control electronics 740. In one embodiment, the waveform is asquare wave, and an electrode potential difference between a firstelectrode and a second electrode can vary between about −2 Volts toabout +2 Volts.

In another embodiment, the waveform, as measured with respect to groundat a first electrode, varies from 0 Volts to a positive voltage, and thewaveform, as measured with respect to ground at a second electrode,varies from 0 Volts to a negative voltage. In another embodiment, thewaveform, as measured with respect to ground or another reference levelat either a first or a second electrode, varies from about 0 Volts toabout 2 Volts; and in some embodiments, these two waveforms may be outof phase with each other such that the potential difference measuredbetween the two electrodes is nonzero. In one embodiment, the frequencyof the waveform is 100 Hz, or from about 0.1 Hz to about 1,000 Hz, orfrom about 0.001 Hz to about 100 KHz, or any amount or rangetherebetween.

In embodiments wherein the variable transmittance optical filtercomprises multiple pairs of electrodes located in different regions, thecontrol circuit may be configured to selectably apply the same voltagesor different voltages, at the same or different times, to differentpairs of electrodes. This may facilitate regional control over variabletransmittance in different regions of the variable transmittance opticalfilter.

4. Additional Components of the Variable Transmittance Optical Filter

The variable transmittance optical filter with an SC electrode systemmay comprise one or more UV blockers to block some or a substantialamount of the UV light that the variable transmittance optical filter ofthe invention is exposed to in order to counteract UV light-induceddegradation of the transition material. For example, in some embodimentswhere the variable transmittance optical filter of the inventioncomprises a hybrid P/E switching material, the variable transmittancefilter requires UV radiation in order to transition to its dark state,however, as is appreciated by persons of skill in the art, chromophores,particularly organic ones, can degrade in UV light. To counter the UVlight-induced degradation of the chromophores, one or more UV blockerscan be used to block some or a substantial amount of the UV light thatthe variable transmittance optical filter of the invention is exposedto. The purpose of the UV blocker in these embodiments is to block asubstantial amount of the UV light from reaching the transition materialwhile allowing sufficient levels of UV radiation exposure to effectautodarkening. Variable transmittance optical filters comprising atransition material that is a liquid crystal material or suspendedparticle material may also benefit from the inclusion of one or more UVblockers. In contrast, when the variable transmittance optical filtercomprises a transition material that is an inorganic material such as aninorganic electrochromic material, UV blocker may be less important.

The UV blocker may be incorporated in the substrate or applied as alayer on the substrate so as to block the transition material of thevariable transmittance from the UV light. If the UV blocker is presentas a UV blocking layer on the variable transmittance optical filter, itmay comprise a film or layer of inorganic material, organic material ora combination of the two. Examples of inorganic materials are titaniumdioxide, zinc oxide, cadmium oxide, tungsten trioxide, or a combinationthereof. An inorganic UV blocking layer can be applied to the substrateby a variety of means such as chemical vapor deposition, physical vapordeposition, (e.g. sputtering, electron beam evaporation, and ionplating), plasma spray techniques or sol-gel processes. A UV blocker canbe provided by a stack of thin film materials, (dichroic stack), withthickness and index of refraction chosen so as to reflect or absorb UVlight. AUV blocker may be made up of a layer of polymer material that isinherently absorbing of the wavelength of light of interest or containslight absorber or stabilizer materials mixed, (dissolved orinterspersed) into the polymer material or covalently bonded to thepolymer itself. Examples of polymer materials include polyethylenes,polypropylenes, polybutylenes, epoxies, acrylics, urethanes, vinylsincluding polyvinyl chloride, poly(vinyl butyral)s, poly(vinylalcohol)s, acetates, polystyrenes, polyimides, polyamides, fluorocarbonpolymers, polyesters, polycarbonates, poly(methyl methacrylate),poly(ethyl methacrylate), poly(vinyl acetate), co-polymers of theaforementioned, and polymer blends of the aforementioned polymers.

A large number of light absorbers and/or stabilizer materials are knownin the art and particularly useful ones include benzotriazoles,benzophenones, cyanoacrylates, hindered amines, oxalanilides andsubstituted triazines.

In embodiments where the variable transmittance optical filter with anSC electrode system comprises a hybrid P/E switching material, theconcentration of UV light absorbers in the UV blocking layer and/or thethickness of the UV blocking layer are chosen so as to provide stabilityagainst sunlight degradation of the transition material layer beyond theUV blocking layer(s), while allowing sufficient levels of UV lightexposure to effect auto-darkening. In one embodiment, the UV blockingfilm blocks more of the UV light below a certain wavelength. The UVblocking film blocks out the damaging high-energy UV at lowerwavelengths, while allowing more of the lower energy UV light to passthrough. The lower-energy UV light can be used to cause theauto-darkening. In one embodiment, the UV blocking film blocks most ofthe UV light below about 350 nm, but allows UV light between 350 nm to400 nm to pass through. Examples of UV absorbing films that may be usedin such embodiments include (EnergyFilm™ (described in WO2002/018132)and EnerLogic™ (described in WO2009/087575). Examples of UV blockinglayers include optical clear pressure sensitive adhesives with UVblocking components (e.g. 8172PCL from 3M) that may be used to affix avariable transmittance optical filter to a surface.

Other coatings or materials that may be applied to a variabletransmittance optical filter according to various embodiments include ananti-abrasion layer, an anti-reflective layer, an infra-red reflectivelayer, UV reflective layer, UV absorbing layer, hydrophobic coatinglayer, hydrophilic coating layer, self-cleaning coating layer or thelike. The UV blocker may block most of the UV light below about 350 nm,or below about 365 nm, or below about 375 nm, or below about 380 nm, orbelow about 385 nm. In some embodiments, the UV blocker is a componentof a substrate; for example, PET, with a UV blocking component (e.g.XST6578 from DuPont Teijin).

In some embodiments, the variable transmittance optical filter accordingto various embodiments of the invention may be disposed upon a pane ofglass or other transparent material suitable for use as a window(“window material”), or incorporated into an insulated glazing unit(IGU), or a storm window, insert window or secondary glazing. Methods ofmaking IGU, windows or the like and affixing an optical filter to glassor other suitable materials are described in the art. The opticalfilters may be applied to the window material using an optically clearadhesive; in other embodiments the second layer comprising thetransition material may first be applied to the window material, and thefirst layer comprising the first substantially transparent substratewith the SC electrode system disposed thereon applied to the secondlayer, thereby assembling the variable transmittance optical filterdirectly on the window material. The window material with optical filtermay subsequently be used in assembly of an IGU according to knownmethods.

In some embodiments, the variable transmittance optical filtercomprising a hybrid P/E switching material has a low power requirement,making it particularly suitable for mobile devices (e.g. those notcoupled to a conventional AC power supply), such as automotive glassapplications, adjustable mirrors, auto-darkening sunroofs or the like,or opthalmic devices.

The variable transmittance optical filter comprises a SC electrodesystem that is in contact with the hybrid P/E switching material. Theelectrodes of the SC electrode system are disposed on the surface of thesame substantially transparent substrate. Leads are connected to eachelectrode in order to apply a voltage to the hybrid P/E switchingmaterial. When an electric voltage is applied to the hybrid P/Eswitching material when it is in its dark state, the switching materiallightens and transmits a greater percentage of incident visible lightuntil it reaches a light state. Control electronics allow a user tocontrol when and how much voltage to apply to the filter. In thismanner, the components of the optical filter of the present inventionprovide for an optical filter that can be in a light state or a darkstate, that can automatically go into its dark state when exposed to UVlight from the sun but can be switched back to a lighter state throughapplication of an electric voltage when desired.

Embodiments of the invention include optical filters that can alsoreduce transmission of light in the UV portion of the spectrum. In oneembodiment, UV light transmittance of the optical filter of theinvention is less than 30%. In another embodiment of the invention, theUV light transmittance of the optical filter is less than 20%. In afurther embodiment of the invention, the UV light transmittance of theoptical filter is less than 10%. In another embodiment of the invention,the UV light transmittance of the optical filter is less than 5%. Asdiscussed, minimal electric voltage is required and only to effectlightening of the variable transmittance optical filter comprising ahybrid P/E switching material of the invention. Maintaining the opticalfilter in a stable state does not require constant application ofvoltage. Rather, any lightening required to adjust for auto-darkening,when in the presence of UV or solar radiation, can be made byintermittent application of voltage to maintain a constant light state,or by applying a reduced amount of voltage. In this way, the amount ofpower consumed by the optical filter is minimized. In addition, theminimal voltage requirements of the optical filters of the inventionmake them amenable to sheet materials having a wide range of sheetresistances as described herein. Thus, optical filters of the presentinvention are amenable to interdigitated electrodes made from conductivematerial having sheet resistances ranging between about 1 Ohms/square toabout 10,000,000 Ohms/square, or any amount or range therebetween,including those exemplified herein.

Process for Preparing the Variable Transmittance Optical Filter

The variable transmittance optical filters described herein are suitablefor manufacturing switchable windows, for example, “smart” windows withfewer components. By forming interdigitated first and second electrodesonto one transparent conductive substrate, a second substrate comprisinga conductive layer used in “smart” window applications may not berequired. Thus, in some embodiments of the variable transmittanceoptical filter, a second transparent conductive substrate is replacedwith a much lower cost nonconductive substrate.

In some embodiments, a bus bar can be applied to one edge of a substratein order to provide an electrical connection. Bus bars can be formedfrom a conducting material such as copper, aluminum, silver, gold, orother conductive materials. A bus bar can be printed on using forexample a silver epoxy or silver ink material. A bus bar can also beformed using copper tape with conductive adhesive. Electrical leads canbe attached to the bus bar.

The variable transmittance optical filters may be prepared according tomethods known in the art. For example, roll-to-roll processing methodscan be used for making the variable transmittance optical filter.Roll-to-roll methods may be particularly suited to production offlexible optical filters in the form of films, for example. Such methodsgenerally comprise the steps of a) providing a flexible substantiallytransparent substrate, b) disposing a transparent conductive material onone side of the flexible transparent substrate, c) forming the SCelectrode system in the transparent conducting material, and d)disposing the transition material in contact with the SC electrodesystem. In embodiments where the variable transmittance optical filtercomprises a first and third layer, the method further comprises the stepof e) providing a second flexible substrate on top of the transitionmaterial; forming a “sandwich” structure with the transition material incontact with the SC electrode system and the two substantiallytransparent substrates. Where the substrate including a transparentconductive layer is available, the step of b) disposing a transparentconductive material may be forgone, and the method may proceed with thestep c) of forming the SC electrode system thereon. Similarly, where thesubstrate is available “pre-printed” with an SC electrode system, thestep c) of forming the SC electrode system may be forgone, and themethod may proceed with the step d) of disposing the transition materialthereon.

In some embodiments where the transition material is a hybrid P/Eswitching material, the formulation comprising same may have a viscosityat room temperature that is too viscous to be readily applied, thus theformulation may be made into a lower-viscosity liquid by heating toallow it to be applied or coated onto the substrates. For example, theswitching material may be heated to a temperature of about 60° C. toabout 80° C. and pressed between the first substrate and optional thirdsubstrate. In some embodiments, the formulation may further comprise aco-solvent to facilitate coating in a roll-to-roll processing method,allowing the switching material to be cast as a liquid and then furthertreated to increase the viscosity of the material to form a gel. Forexample, the hybrid P/E transition material can be dried wherein thesolvent and/or co-solvent is evaporated from the hybrid P/E switchingmaterial. In other embodiments, the hybrid P/E switching material maycomprise one or more component that can be cross-linked and/orpolymerized, and cured to increase the viscosity, and/or to form a gel.Curing the hybrid photochromic/electrochromic transition material may beaccomplished, for example, with UV light. A photoinitiator may be addedto the switchable material which, when exposed to UV light, can help tocross-link the formulation to increase its viscosity. Other methods ofcuring such as with heat or exposure to electron beams may be possiblewith different formulations. One skilled in the art will appreciate thatthis polymerization and/or crosslinking can be initiated by chemical-,thermal-, or photo-type initiators. A common method of UV curing can beaccomplished by adding a constituent that, when exposed to UV light,will form a radical to initiate polymerization and/or cross-linking.Suitable polymerization initiators are known in the art and include, forexample, heat sensitive initiators such as AIBN, photo-initiators suchas DAROCUR 4265. The gelled hybrid photochromic/electrochromictransition material can then adhere to both substrates to form anintegral structure.

Once the filter has been made, it can be cut to size, sealed around theperimeter if necessary, and an electrical connection can be made to theelectrodes. The electrical connection can be made by printing bus barsonto the substrate in contact with the transparent conductive coating.Electrical leads can then be attached to the bus bars. The variabletransmittance optical filter with the SC electrode system when completedwill transition from one state of visible light transmittance to anotherwhen an appropriate electrical charge is applied to the electrodes.

Testing the Optical Filter

The performance efficacy of the variable transmittance optical filterswith an SC electrode system according to the present invention can betested to determine characteristics such as, for example, the amount ofvisible light transmittance, haze, switching speed, sheet resistancephotostability, polarity cycling, and voltage requirements. Thesecharacteristics can be determined using standard techniques known in theart.

Clarity in optical filters can be caused by transmission haze due tocloudiness caused by scattering of light. Light may be scattered byparticles that are suspended in the substance. Haze may be measured bymethods known in the art, for example, using a “hazemeter” (e.g. XL-211Hazegard, BYK Gardner), according to known and/or standardized methods.Optionally, the haze of the optical filters according to variousembodiments is between about 0% and about 5%. In some embodiments of theinvention, the optical filter has a haze transmission of about 5% orless, about 3% or less, about 2% or less, about 1.5% or less, or about1% or less; or from about 0 to about 2%, or from about 0.5% to about 3%,or any amount or range therebetween.

“Switching time” (“switching speed”) refers to the time necessary for amaterial to transition from a dark state to a clear state, or from aclear state to a dark state, or to alter light transmission by a definedamount (e.g. 60% to 10% VLT in 5 minutes) Generally the optical filtersof the present invention will have a darkening time of between about 1second and 30 minutes to reach about 10% of the VLT of the dark statefrom the lightened state, and a lightening time of between about 1second and 30 minutes to reach about 90% of the VLT of the light statefrom the darkened state. In some embodiments of the invention, thedarkening time and lightening time of the optical filter mayindependently be from about 0.5 minutes (30 seconds) to about 5 minutes,or any amount or range therebetween, for example 0.5, 1, 1.5, 2, 2.5, 3,3.5, 4, 4.5 or 5 minutes, or any amount of time or range therebetween.

In some embodiments where the variable transmittance optical filter withan SC electrode system according to the present invention comprises ahybrid P/E switching material, the switching of the hybrid P/E switchingmaterial from the dark state to the light state over the electrodeconnected to the positive potential (anode) progresses more rapidly thanthe switching of the transition material from the dark state to thelight state over the electrode connected to the negative potential(cathode).

In some embodiments, where the variable transmittance optical filterwith an SC electrode system according to the present invention comprisesa hybrid P/E switching material, and the polarities of the appliedvoltage is switched, the hybrid P/E switching material over theelectrode connected to the negative potential completes the transitionfrom the dark state to the light state within 30 minutes, or within 10minutes, or within 5 minutes, or within 3 minutes, or within 1 minute,or within 30 seconds of reversing the polarity of the voltage.

Uses of the Variable Transmittance Optical Filter

The variable transmittance optical filters of the present invention canbe incorporated into a variety of applications, including devices orsystems where it is desirable to dynamically control and filter light.The variable transmittance optical filters comprising first and secondlayers may applied or laminated onto another substrate. Exemplaryapplications include architectural windows, vehicle (automobile, bus,train, plane, boat, ship or the like) windows, windscreens or visors,ophthalmic devices and the like. It is also contemplated that in someembodiments different regions of such architectural windows, automotivewindows, and ophthalmic devices can be controlled individually, or ingroups, by designing the variable transmittance to include multiplepairs of electrodes that can be individual controlled.

1. Variable Transmittance Windows

Variable transmittance optical filters of the present invention can beincorporated into a variety of window systems such as, for example,architectural smart window systems, or automotive window systems, toconfer controllable variable transmittance functionality on the windowsystem. As described herein, the variable transmittance optical filterwith the SC electrode system according to the invention can be made witha first layer and optionally a third layer that comprises rigid orflexible, substantially transparent substrate(s). When the variabletransmittance optical filter is prepared with one or two rigidsubstantially transparent substrates, the variable transmittance opticalfilter can be directly incorporated into the structure of the windowsystem. Alternatively, when the variable transmittance optical filter isprepared with one or two flexible substantially transparent substrates,the variable transmittance optical filter can be laminated onto a rigidsubstantially transparent substrate that is incorporated into the windowsystem. The rigid transparent substrate may be flat, or curved (e.g. acurved window). Electrical leads are connected to the SC electrodesystem of the variable transmittance optical filter. The electrodes arein contact with the transition material of the variable transmittanceoptical filter and when a voltage is applied to the electrodes thetransition material transitions from one state of visible lighttransmittance to another. Such window systems, when comprising a hybridP/E material will darken when exposed to UV or sunlight, and lightenwhen an electric voltage is applied. The controlled reduction of the VLTof the window may be useful by reducing glare, and/or reducing solarheat gain, and/or improve occupant comfort.

A variable transmittance window for a vehicle may have a relative darktint even in the light state—a dark tint may be beneficial for reducingsolar heat gain inside the vehicle, improve fuel efficiency by reducinga user's need for air conditioning, and/or provide visual privacy. Inone embodiment, a variable transmittance window for a vehicle may have aVLT from about 0% to about 20% in the dark state, or any range or amounttherebetween, for example 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19 or 20%; and from about 5% to about 30% in thelight state, or any range or amount therebetween, for example 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,26, 27, 28, 2 or 30%. In some embodiments, the vehicle window may havedark and light state VLTs with a contrast ratio of at least 2:1, 3:1,4:1, 5:1 or any amount or range therebetween.

Two or more variable transmittance windows in a vehicle may have thesame, or different VLT in light and dark states, and/or same ordifferent contrast ratios. For example, a vehicle may have a sunroofwith about 5% VLT in a dark state and about 15% in a light state (˜3:1contrast ratio), while a side or rear window may have about 15% VLT in adark state and about 60% VLT in a light state (˜4:1 contrast ratio).Greater VLT and/or a higher contrast ratio may provide increasedvisibility. This may be desirable to provide vehicle passengers with abetter view outside. For front (windshield) and side-front windows wheredriver visibility is of greater importance, a variable transmittancewindow with greater VLT than is used in the rest of the vehicle windowsmay be selected. In one embodiment, front side window has a visiblelight transmittance of 20% in the dark state and 80% in the light state.In some embodiments, a portion of the window of the vehicle may comprisea portion that has variable transmittance. For example a top portion ofa front window may comprise a variable transmittance optical filter thatdarkens with exposure to sunlight, and may be cleared automatically withapplication of a voltage when a light sensor indicates reduced lightoutside, or in response to a drivers preference by activation of aswitch to initiate application of a voltage. For a vehicle with multiplevariable transmittance windows, each window may be independentlycontrolled, or the multiple windows may be simultaneously controlled asa group via a control system.

The substrate for a variable transmittance window for a vehicle may betempered glass, polycarbonate, acrylic or the like. A variabletransmittance window for a vehicle comprise a variable transmittanceoptical filter \ comprising a transition material and an SC electrodesystem. The transition material may comprise a hybrid P/E compound. Thevariable transmittance window may further comprise a power source, suchas an energy harvesting power source, and an electrical systemconfigured to receive power from the power source and to provide avoltage to a first electrode and a second electrode of the variabletransmittance optical filter. The variable transmittance window mayfurther comprise a frame, such as a generally C-shaped gasketsurrounding the periphery of the window. Electrical system and powersources, including energy harvesting power sources as described hereinmay be used in the variable transmittance window. A variabletransmittance optical filter may be laminated to one side of the windowusing an adhesive, such as 8172 PCL, as described herein. Alternately, avariable transmittance optical filter may be laminated between twosubstrates with PVB or EVA interlayers, as described above.

The variable transmittance window may automatically darken when exposedto UV light (for embodiment where the switching material is a hybrid P/Eswitching material). Activation of a switch (e.g. by control electronicsor by a user) applies power from the power source to the first andsecond electrodes of the variable transmittance window and fades thewindow. Windows with variable tinting may be advantageous in that itreduces solar heat gain inside the vehicle, and reduces glare, but canbe faded where more light or visibility through the window is desired. Avariable tint window may eliminate the need for an opaque blind to blockoff the sunroof.

2. Variable Transmittance Ophthalmic Device

Variable transmittance optical filters of the present invention can beincorporated as a variable transmittance lens in a variety of ophthalmicdevices. Variable transmittance ophthalmic devices of the invention willtransition from one state of visible light transmittance to another withthe application of an electric charge. In some embodiments, where thevariable transmittance optical filter comprises a hybridphotochromic/electrochromic, the variable transmittance ophthalmicdevices will darken automatically when exposed to UV or in sunlight andwill lighten through application of an electric charge. For example, thevariable transmittance optical filters of the invention can beincorporated as a variable transmittance lens in sunglasses, sportseyewear such as ski goggles and cycling glasses, industrial uses such assafety eyewear, and others.

The variable transmittance optical filter according to variousembodiments of the invention can be incorporated into ophthalmic devicesin a variety of ways. A flat lens may incorporate an optical filter byapplication of a variable transmission optical filter comprising aflexible substrate to a surface of the lens material (e.g. the lensmaterial may comprise the optional third layer of some embodiments asdescribed herein). A curved or spherical lens may incorporate an opticalfilter. Such a lens may comprise a first substrate that is molded, cast,vacuum formed, or thermoformed into a suitable shape, according to knownmethods. A layer of conductive material may be coated onto the formedfirst substrate, and an SC electrode system of suitable layout etchedinto the conductive material. A layer of transition material may besubsequently applied, followed by lamination or adherence of a secondsubstrate shaped to complement the first substrate and transitionmaterial may be applied and sealed as necessary; connectors forconnecting bus bars, electrodes and the like to a control system may besubsequently applied. The SC electrode system may comprise any suitablelayout—a circumferential layout of first and second electrodes isillustrated in FIG. 9 for the lens of goggles of FIG. 10.

Referring to FIG. 9, an SC electrode system according to anotherembodiment of the invention is shown generally at 230. First 232 andsecond 234 circumferential electrodes follow a coiling path generallyconforming to the shape of the substrate. For this embodiment, thevariable transmittance may be cut to a suitable lens shape, forincorporation into an opthalmic device, such as that illustrated in FIG.10. Contact points 236, 238 at electrode ends may connect the lens toleads (not shown) connected to an electrical system to provide voltageto be applied to the first and second electrodes. Referring to FIG. 10,an opthalmic device according to various embodiments of the invention isshown generally at 250. A variable transmittance lens 252 comprisingfirst and second electrodes of an SC electrode system is held in a frame254, the frame configured to position the lens 252 in front of the eyeswhen in use. A strap 256 may hold the opthalmic device on a user's headwhen in use. A compartment in the frame 254 contains a power source 258.To operate the device, a user may depress a button 260 to close a switchof the control electronics 262 of an electrical system comprising aportion of the SC electrode system and provide a voltage from the powersource 258 to the first and second electrodes, and the variabletransmittance optical filter transitions from a dark state to a fadedstate.

Embodiments of the invention are illustrated, in part, by the followingnon-limiting methods and examples:

EXAMPLES Example 1 Preparation of Selected Hybrid P/E Compounds

S001 and S002 were prepared as described in U.S. Pat. No. 7,777,055.

Synthesis of S042—

Synthesis of 3-bromo-2,5-bis(4-(tert-butyl)phenyl)thiophene: (30)

Sodium carbonate monohydrate (58.0 g, 468 mmol) was dissolved in water(500 mL) and a solution of 4-(tert-butyl)-phenylboronic acid (40.0 g)and 2,3,5-tribromothiophene (30.0 g, 94 mmol) in THF (500 mL) was added,and deoxygenated by bubbling with argon. Pd(PPh₃)₄ (5.0 g, 4.30 mmol)was added and the mixture refluxed for 24 h. The mixture was cooled andthe aqueous phase separated and extracted with EtOAc. Organic fractionswere combined washed with water (500 mL) and dried over MgSO₄. Thesolvent was evaporated and the crude product washed in MeOH, filteredand dried overnight to afford a light yellow, powdery solid (35.46 g,89%).

Synthesis of S042

(3,3′-(perfluorocyclopent-1-ene-1,2-diyl)bis(2,5-bis(4-(tert-butyl)phenyl)thiophene.):A solution of (30) in anhydrous THF/ether cooled to −45° C. and treatedwith nBu-Li_(2.5 M in hexanes, 35 mL, 87 mmol) dropwise under a n argonatmosphere. The reaction mixture was stirred for a further 15 minutesfollowed by addition of octafluorocyclopentene (5.6 mL, 41.5 mmol) usinga cooled gas tight syringe. The reaction was allowed to stir until thetemperature reached −10° C., quenched by the addition of 10% HCl (50mL). The aqueous layer was separated and extracted with ether. Theorganic phases were separated and pooled, dried over MgSO₄, filtered andsolvent removed by rotary evaporation. The crude product was stirred inMeOH for 3 hours, and the resulting precipitate filtered, dried andpurified using flash chromatography (hexanes), affording 2 fractions—F1was pure S006 (TLC), F2 contained S006 along with a fluorescentbyproduct by TLC. F1, 5.35 g, 14.8%) and F2, 10.4 g (˜75% pure, 22%) aslight yellow, powdery solids. ¹H NMR (400 MHz, CDCl₃) δ 7.37 (d, J=8.5Hz, 4H), 7.30 (d, J=8.5 Hz, 4H), 7.05 (d, J=8.4 Hz, 4H), 6.92 (d, J=8.4Hz, 4H), 6.13 (s, 2H), 1.34 (s, 18H), 0.91 (s, 18H).

Synthesis ofS054—3,3′-(perfluorocyclopent-1-ene-1,2-diyl)bis(2,5-bis(4-methoxyphenyl)thiophene)

Synthesis of 3-bromo-2,5-bis(4-methoxyphenyl)thiophene (37)

2,3,5-Tribromothiophene (6.42 g, 20 mmol), 4-methoxyphenylboronic acid(6.38 g, 42 mmol) and sodium carbonate (8.5 g, 80 mmol) were stirred inTHF/water mixture (125/50 ml) for 90 min at RT under argon flushing.Pd(PPh₃)₄ (693 mg, 0.6 mmol) was added. The mixture was refluxed for 16h (TLC), cooled to RT and THF was removed by evaporation. Water wasadded and aqueous fractions extracted with EtOAc. The organic fractionswere combined, solvent removed and the crude product purified by flashchromatography (Silica gel; hexane/chloroform/EtOAc; gradient up to 20%chloroform then 20% EtOAc) to yield3-bromo-2,5-bis(4-methoxyphenyl)thiophene (4.9 g, 13 mmol, 65%).

Synthesis of S054: Compound (37)

(10.64 g; 28.4 mmol) was dissolved in anhydrous ether (350 mL) andcooled to −25° C. n-BuLi (14.2 mL; 35.5 mmol; 2.5 M in hexane) wasadded. The mixture was stirred at this temperature for 0.5 h.Octafluorocyclopentene (1.9 mL; 14.2 mmol) was added in two portions,and the reaction was allowed to warm slowly over 3 h. The reaction wasquenched by addition of 10% aqueous HCl (50 mL). Organic layer wasseparated and the aqueous was extracted with EtOAc (250 mL). Solventfrom the combined organic extracts was evaporated and crude material waspurified by column chromatography (Silica gel; hexanes/EtOAc up to 30%).Collected product was sonicated in methanol and pale yellow powder wasfiltered and dried in air (4.46 g; 5.82 mmol; yield 41%). ¹H NMR (400MHz, CDCl₃) δ 7.32 (d, J=8.7 Hz, 4H), 6.91 (dd, J=8.7, 2.4 Hz, 9H), 6.60(d, J=8.6 Hz, 4H), 6.25 (s, 2H), 3.85 (s, 6H), 3.41 (s, 6H).

Synthesis ofS068—12,12′-((4,4′-(perfluorocyclopent-1-ene-1,2-diyl)bis(5-(4-(tert-butyl)phenyl)thiophene-4,2-diyl))bis(4,1-phenylene))bis(12-methyl-2,5,8,11-tetraoxatridecane)

Synthesis of 2-(2-(2-methoxyethoxy)ethoxy)ethyl 4-methylbenzenesulfonate (46)

To a solution of p-toluenesulfonyl chloride (3.17 g, 19.3 mmol) in 20 mLof pyridine was added 2-(2-(2-methoxyethoxy)ethoxy)ethanol (4 g, 21mmol), stirred at 0° C. for 12 h and at RT for 2 h. To this suspension,water and hexanes and ethyl acetate were added and separated. Theorganic layer was neutralized with dilute HCl and separated again;organic fractions were pooled, dried (MgSO₄ and NaHCO₃), filtered, andconcentrated under reduced pressure to give 4.87 g, 15.3 mmol (79%) of2-(2-(2-methoxyethoxy)ethoxy)-ethyl 4-methylbenzene sulfonate as acolorless oil.

Synthesis of S068

Sodium hydride (0.24 g, 6 mmol, 60% dispersion in oil) was washed withhexanes (6 mL) and a solution of di-alcohol S067 (1.33 g, 1.52 mmol) inTHF (25 mL) was added under argon. The reaction mixture was stirred for1 h at RT. To the resulting suspension was added a solution of (46)(1.06 g, 3.35 mmol) in anhydrous dimethylformamide (12 mL) in oneportion and the mixture was stirred for 48 h. The reaction was quenchedby addition of brine (100 mL) and extracted with EtOAc (3×100 mL). Theorganics were combined, washed with water (2×100 mL), dried over MgSO₄,filtered and evaporated to dryness. The residue was purified by columnchromatography (Silica gel; hexane/EtOAc (50/50) as the eluent to obtain1.24 g (1.06 mmol; 70%). ¹H NMR (400 MHz, CDCl₃) δ 7.44 (d, J=8.4 Hz,4H), 7.36 (d, J=8.4 Hz, 4H), 7.09 (d, J=8.4 Hz, 4H), 6.96 (d, J=8.3 Hz,4H), 6.21 (s, 2H), 3.72-3.68 (m, 12H), 3.66 (t, J=5.3 Hz, 5H), 3.61-3.57(m, 4H), 3.43-3.37 (m, 10H), 1.58 (s, 12H), 0.95 (s, 18H).

Example 2 Preparation and Testing of Variable Transmittance OpticalFilters with an Interdigitated SC Electrode System Comprising SymmetricElectrode Widths

Six variable transmittance optical filters comprising differentinterdigitated SC electrode systems were prepared as follows. A testwafer was formed from a piece of ITO-coated glass purchased from DeltaTechnologies (Stillwater, Minn.). Areas with symmetric interdigitatedelectrodes were created in which both first and second electrodes andbus bars were of equal size, with spacing and electrode digit width asindicated in Table 1. A photoresist layout of the electrode patterns wascreated with CAD, a suitable photomask produced and the patternwet-etched into the ITO coating using standard photolithographictechniques. Briefly, the substrate was cleaned with acetone andisopropyl alcohol, and AZ™ MIR™ 703 resist spincoated at 4000 rpm andbaked at 90° C. for 60 seconds (following manufacturer's instructions).The electrode patterns were exposed through the photomask (chrome onglass), and the substrate baked again at 110° C. for 60 seconds. Thesubstrate was then developed in AZ™ MIF™ 300 for 60 seconds, and etchedfor 4.5 minutes in 37% HCl, and rinsed to remove etchant. Remainingresist was removed with acetone.

TABLE 1 SC Electrode device numbers and dimensions of symmetricelectrodes Device # Spacing A (mm) Digit width B (mm) 1 0.5 1 2 0.25 0.53 0.1 0.1 4 0.05 0.05 5 0.025 0.025 6 0.015 0.015

To construct the SC electrode devices, a hybrid P/E switching material(according to Formulation 9—see Example 4) was then added. A drop offormulation was placed on the device to be tested and a small glasscover slip was placed he formulation distributed to a uniform layer withapplication of the cover slipon top of each one of the interdigitatedpatterns and a plain glass slide (a second substrate) was added on topto form the variable transmittance optical filter. The switchingmaterial was darkened with UV light for 1 minute, and then bleached withelectricity by applying approximate two volts DC across the twoelectrodes of the SC electrode system via the bus bars for approximately30 seconds to five minutes by electrical leads from a power source tothe bus bars of the electrodes.

All of devices 1-6 demonstrated successful electrofading of theswitching material, however improved uniformity of fading of the deviceswas observed in devices with narrower electrodes. Devices 1 and 2demonstrated electrofading initially over the anode, such that theinterdigitated electrode pattern was highlighted by the lighter anddarker portions of the hybrid P/E switching material. Device 3demonstrated electrofading over the anode and mostly over the cathodes,although some faint lines of darkened material were still visible overthe cathode. In devices 4, 5, and 6, fading was more uniform

Example 3 Preparation and Testing of Variable Transmittance OpticalFilters with an SC Electrode System Comprising Asymmetric ElectrodeWidths

This example describes the preparation and testing of variabletransmittance optical filters in which the SC electrode system of thevariable transmittance optical system is patterned asymmetrically. Afirst electrode comprises fingers that are wider than those of thesecond electrode, providing a greater square area for the firstelectrode relative to the second electrode. In devices comprising ahybrid P/E switching material where the larger electrode is the anode(positive potential) and the smaller electrode is the cathode (negativepotential), all, or substantially all, of the area of the device can beelectrofaded. This example demonstrates that an asymmetricinterdigitated electrode pattern can provide better uniformity whileelectrofading the switching material, with a smaller electrode area, andin some applications, a reduced need for etching thin electrodes.

Six devices were prepared as described for Example 2, with Formulation#9. Electrode configuration are set out for devices 7-12 in Table 2.Devices were exposed to UV light for 1 minute to darken the hybrid P/Eformulation.

TABLE 2 SC Electrode devices and dimensions of asymmetric electrodesSpacing A Digit width B1 Digit Width B2 B1/B2 Device # (mm) (mm) (mm) %area 7 0.05 1 0.05 90.9/4.5  8 0.05 1 0.5  64.5/32.25 9 0.05 1 0.186.9/8.7  10 0.05 1 0.2 80/16 11 0.05 1 0.3  74/22.2 12 0.03 1 0.0394.3/1.06

FIG. 11 is a photograph of devices 7-12, after electrofading of theUV-darkened devices for 30 seconds to 1 minute. Positive voltage wasapplied to the first electrode (1 mm digit width for all devices) and anegative voltage to the second (narrower) electrode cathode. Fading ofthe hybrid P/E switching material to a clear state occurred first overthe anode electrode for all of devices 7-12. In the devices with a verythin cathode (e.g. device 12 and device 7), the fading spread over theentire device quickly to give good uniformity, and the devices werefully faded in about 20 seconds. Device 9 also demonstrated fading overthe entire device but took longer for the fading to diffuse over thenegative electrode. Device 10 and 11 did not completely fade over thenegative electrode even after being left for more than one minute.

Example 4 Use of Alternating Voltages to Transition Optical FilterDevices Comprising Asymmetric Electrode Configurations

This example demonstrates the use of alternating polarity of electrodesto improve transition (switching) time of a device comprising a hybridP/E switching material. Devices 7-12 according to Example 2 wereprepared as described. A positive voltage was applied to the largerfirst electrode (anode) and a negative voltage was applied to thenarrower second electrode (cathode). The polarity was reversed onceduring the fading period such that a negative voltage was applied to thelarger first electrode to make it the cathode and a positive voltage wasapplied to the narrower second electrode to make it the anode. Potentialwas applied at each polarity for about 15 to 30 seconds. Devices 7 and 8were tested and both were completely faded to good uniformity withoutstripes in about 30 seconds to one minute by manually switching thepolarity between one and three times during the fading.

Example 5 Preparation of the Hybrid P/E Switching Material

Table 3 sets out formulations for hybrid P/E switching material that maybe used in device of the present working examples. Compounds that may beused in the formulations include those according to Formulae IA/IB, andthose illustrated herein. In some examples, the compound used in aformulation may be S001, or a derivative thereof having a functionalgroups on one or more of the four peripheral thiophene rings; or S002,or a derivative thereof having a functional group on one or more of theperipheral phenyl rings; or S042, or a derivative thereof having anotherfunctional group on one or more of the peripheral phenyl rings; or S054,or a derivative thereof having another functional group on one or moreof the peripheral phenyl rings; or S068, or a derivative thereof havinga functional group on one or more of the peripheral phenyl rings.

PEGDMA, solvents, electrolytes, initiators, charge carriers, cosolvents,polymers and other formulation components are available from commercialsuppliers (e.g. Sigma-Aldrich); or as indicated. DAROCUR™ is availablefrom CIBA Specialty Chemicals of Basel Switzerland, a division of BASF.PVB B-90 is available from Butvar, a division of Solutia Inc. of St.Louis, Mo.

Formulation #2 was prepared for photostationary state (PSS)determination, using 2×10⁻⁵ M of the indicated compound, in a solvent(triglyme).

TABLE 3 Type of Formulation formulation Formulation (% wt of components)component component 1 3 4 5 6 7 8 9 chromophore 3 3 5 3.4 3.4 2 0.5 5solvent triglyme 75 74 72 70.7 70.6 28.8 93.5 cyclopentanone 89tetraglyme GBL electrolyte LiClO4 1 1 1 TBAPF6 1 1 1 0.4 1 polymerPEGDMA860 15 PMMA 15 5 5 PVB B90 22 24.9 25 8.8 initiator DAROCUR 0.01charge carrier TBPA 6 6 HALS A cosolvent THF 60 charge DNB 1 compensatorPB Total (wt %) 100 100 100 100 100 100 100 100

Hybrid P/E compounds used in formulation #1 include S001 or a derivativethereof having different functional groups on the four peripheralthiophene rings, or S002 or a derivative thereof having differentfunctional groups on the four benzene rings.

Hybrid P/E compounds used in formulation #2 include S054 or a derivativethereof having different functional groups on the four benzene rings.

Hybrid P/E compounds used in formulation #3 include S001 or a derivativethereof having different functional groups on the four peripheralthiophene rings, or S002 or S042 or a derivative thereof havingdifferent functional groups on the four benzene rings.

Hybrid P/E compounds used in formulation #4 include S001 or a derivativethereof having different functional groups on the four peripheralthiophene rings, or S054 or a derivative thereof having differentfunctional groups on the four benzene rings.

Hybrid P/E compounds used in formulation #5 include S054 or a derivativethereof having different functional groups on the four benzene rings.

Chromophores used in formulation #6 include S001 or a derivative thereofhaving different functional groups on the four peripheral thiophenerings, or S054 or a derivative thereof having different functionalgroups on the four benzene rings.

Chromophores used in formulation #7 include S054 or a derivative thereofhaving different functional groups on the four benzene rings.

Chromophores used in formulation #8 include S042.

Chromophores used in formulation #9 include S001.

Example 6 Optical Properties of Hybrid P/E Switching Material

The VLT spectrum of formulation #3 comprising S001, S002 or S042, weredetermined for light and dark states. An Ocean Optics spectrometer wasused to measure the % visible light transmittance of the sample, in itslight and dark states, over an electromagnetic spectrum. The formulationis first exposed to UV light to switch to the dark state, decreasing thetransmittance of the material in the visible range between about 400 andabout 750 nm. An electric charge of 2 Volts is then applied to theswitching material sample for 3 minutes, causing the sample to revert toits light state. In the light state, more light is permitted to passthrough the switching material resulting in an increase in percenttransmittance in the range from 400 to 750 nm. An exemplary spectra forS001 demonstrated a VLT in the light state of about 80%, and a VLT inthe dark state was about 20%. This provided a contrast ratio of about 4.

The sensitivity of the formulations to the intensity of UV light wasalso studied. Formulation #2 comprising hybrid P/E compound S054 wasexposed to both UV light at 365 nm and solar radiation (using a solarsimulator) with and without a UV blocking film made by Energy Film ofPortland, Oreg. The Energy Film UV blocking film acts as a band-passfilter and effectively blocks the high intensity UV light (below about365 nm). As illustrated in FIG. 12, depicting the absorbance spectra ofthe switching material under the various UV light intensities, theswitching material maintains sensitivity to the low intensities of UVlight (above about 365 nm) to darken. FIG. 12 shows a plot of theabsorbance spectra in a faded state (solid line); darkened using a 365nm light source without (open circle) or with (open square) EnergyFilm™;and darkened using a solar simulator without (solid circle) or with(solid square) EnergyFilm™. In a faded state (solid line), theabsorbance of the formulation is reduced to baseline. Absorbance reachesa maximum at about 620-240 nm for all sample treatments, with themaximum absorbance varying with light source and presence or absence ofa partial UV blocking layer. Highest absorbance is reached for a UVlight source without EnergyFilm™—about 0.265. Placement of the UVblocking layer between the sample and light source reduces the maximumabsorbance to about 0.254. Simulated full spectrum sunlight provides amaximum absorbance in the dark state of about 0.105; inclusion of the UVblocking layer reduces the maximum absorbance to about 0.055.

Example 7 Preparation of Variable Transmittance Optical Filters with TwoTransparent Conductive Substrates

Examples 7 to 16 as included herein pertain to the preparation andtesting of variable transmittance optical filters comprising twotransparent conductive substrates. The electrodes of these filters arenot substantially co-planar, however, the variable transmittance opticalfilters themselves have been prepared with hybrid P/E switchingmaterials and have been included to demonstrate general properties ofthe hybrid P/E switching materials in the format of this optical filter.

Method A:

An ITO coated PET substrate having a thickness of 7 mil (˜178 microns)and a sheet resistance of 50 ohms/square (OC50, made by CP Films) is cutinto two 15 cm×15 cm sheets. The substrate may be cleaned before use,and is temporarily laminated to glass plates to facilitate handling.Steel spacers are positioned at the perimeter of the PET, to set the gapfor the final pressed device (from 20-70 microns). A volume of switchingmaterial (below, heated to facilitate dispensing), is placed on the PETto completely fill the gap between the PET sheets when the device ispressed. A second piece of glass-backed PET is placed on top, so thatthe PET sheets overlap such that there is some ITO coating exposed, toact as the external electrical contacts. The sandwich(glass-PET-switching material-PET-glass) is placed in the center of apress platens (heated to 45° C.). Pressure greater than 160 psi isapplied to the filter using a Carver hydraulic press, or nip rollers,for a time sufficient to allow the switching material to attain auniform thickness (at least 10 seconds, up to about a minute, or up toseveral hours). After the pressure is released, the glass plates areseparated, any excess switching material is wiped off and conductivetape is applied to the exposed ITO. Total thickness of an optical filter(e.g ITO-coated PET+switching material) is about 16 mil (˜406 microns),including a 2 mil (˜51 microns) layer of switching material

Method B:

An ITO coated PET substrate is prepared as described above. A switchingmaterial comprising a low-boiling solvent (THF) is then coated onto theconductive side of a first sheet of ITO-coated PET using a slot die, aknife coater, or other roll-to-roll coating method (according tomanufacturer's instructions). The thickness of the coater is set suchthat the final coating once the low-boiling solvent is evaporated off isthe desired thickness. For example, to obtain a final switching materialthickness of about 50 microns, the initial wet coating may be set toabout 114 microns. The low-boiling solvent is evaporated from theswitching material using blown air or heat or a combination of both. Asecond layer of ITO-coated PET is laminated on top of the coating withthe conductive side in contact with the switching material to form asandwich structure. The laminated structure is cut to the desired size(if required) and electrical contacts added. An exemplary optical filterproduced in this manner demonstrated a total thickness of about 16 mil(˜406 microns), with a switching material layer of about 2 mil (˜51microns).

Example 8 Visible Light Transmittance (VLT) Determination of the OpticalFilter

The VLT of the optical filter prepared by the method A described inExample 7 comprising formulation #4 with S054 was measured using anOcean Optics spectrometer. Optical filters exposed to 365 nm UV lightfor about 3 minutes had a VLT of 17%. The transmission increased afterapplication of a charge of 2 Volts for about 3 minutes to 69%.

Example 9 Haze Determination of the Optical Filter

The clarity of the optical filter prepared by the method A described inExample 7 comprising formulation #4 with S054 or S001 was measured usinga XL-211 Hazard Hazemeter manufactured by BYK Gardner. The haze of theoptical filter was measured to be about 2%.

Example 10 Switching Speed Determination of the Optical Filter

Switching speed is determined by the amount of time it takes for theoptical filter to go from the dark state to the light state, and viceversa. To transition from the light state to the dark state, the opticalfilter is exposed to 365 nm UV light for 3 minutes before application ofvoltage To transition from the dark state to the light state, a chargeof 2 Volts is applied to the filter for 3 minutes, before exposure tothe light source. Switching time from the light state to the dark stateis measured as the time required to achieve 90% of the VL T of the darkstate from the fully light state. Switching time from the dark state tothe light state is measured as the time required to achieve 90% of theVLT of the light state, from the fully dark state.

The optical filter prepared by the method A described in Example 7comprising switching material according to formulation #4 comprisingS001 or S054, the optical filter including a UV blocking film (EnergyFilm) applied to the glass-back PET opposite to the switching material,was tested. The switching speed of the optical filter was about 30seconds from the light state to the dark state, and about 2 minutes forswitching from the dark state to the light state. The switching speed ofthe optical filter prepared with formulation #1 comprising S001 or S002was measured to be about 35 seconds from the dark state to the lightstate and 2 minutes from the light state to the dark state. Theswitching speed of the optical filter prepared with formulation #7 withS054, is measured to be about 3 minutes 20 seconds from the dark stateto the light state and 12 seconds from the light state to the darkstate. Thus, the switching time for transitioning from the light stateto the dark state may, for some transition material comprising a hybridP/E compound, be different from the switching time for transitioningfrom the dark state to the light state.

Example 11 Photostability Determination of the Optical Filter

Photostability of the optical filter is determined by exposing thesamples to UV light similar to the UV light in the solar spectrum.Samples are tested at regular intervals to determine degradation. Whenthe contrast ratio has dropped to 50% of the original contrast ratio ofthe device (determined prior to testing), the device is considered tohave failed. The photostability of the optical filters is determinedusing a QUV accelerated weathering tester from Q-Labs. Photostability ofthe optical filter is also determined using an S16 accelerated testinginstrument from Solar Light to test the photostability of the opticalfilter at higher power densities.

The photostability of the optical filter made according to the methoddescribed in Example 7 comprising formulation #5 using S054 was testedon a QUV for 1300 hours at about 7.3 mW/cm² before 50% degradation wasreached. The same optical filter was tested on a Solar Light unit at 135mW/cm² for 540 hours before 50% degradation was reached.

Example 12 Cycling Durability Determination of the Optical Filter

Cycling durability is determined by exposing the optical filter tocontinuous UV light using a Spectroline transilluminator and applying avoltage to the optical filter at regular time intervals. First, theamount of time required to darken and lighten the optical filter isdetermined. This is then used to determine how much time the voltageshould be turned on and off for in the automated test. Typically, thevoltage “on” time is set to be the amount of time it takes for theoptical filter to bleach to about 90% of its initial value. The voltage“off” time is set to be the amount of time it takes for the opticalfilter to darken to 90% of its original value. The cycling is thencontrolled by an automated cycling set-up using a PC, a LabJackinstrument (available from LabJack Corporation of Lakewood Colo.). Inthe “off” state, the two electrodes are shorted together to dissipatethe charge on the optical filter.

The cycling durability of the optical filter made according to themethod described in Example 7 comprising formulation #6 comprising S054,with a UV blocking film (Energy Film) applied to the glass-backed PETopposite to the switching material, was tested. To observe the effect ofambient atmosphere on the durability of the device, a first preparationof the formulation (6-1) was prepared at the bench (exposed to ambientatmosphere), and a second preparation of the formulation (6-2 wasprepared in an oxygen-free atmosphere (glove box). The optical filtercomprising formulation 6-1 demonstrated 741 switching cycles beforereaching a 50% degradation point (the contrast ratio decreased to 50% ofthe starting contrast ratio). In comparison, the optical filtercomprising formulation 6-2 demonstrated 1553 cycles before reaching a50% degradation point).

Example 13 Sheet Resistance Determination of the Optical Filter

The operability of optical filters using substrates of different sheetresistances was tested. Optical filters were made according to themethod described in Example 7 comprising formulation #4 with S001 orS054, and ITO-coated substrates of 50 Ohms/square, 100 Ohms/square, and300 Ohms/square. Optical filters were also made according to the methoddescribed in Example 6 comprising formulation #8 with S042, andITO-coated substrates of 1,000 Ohms/square, and 100,000 Ohms/square. Theoptical filters were tested for the ability to transition between lightand dark states. In all examples the optical filters were still able tolighten upon application of electricity. Optical filters with lowersheet resistances were observed to switch faster.

Example 14 Required Voltage Determination of the Optical Filter

To determine the minimal voltage required to cause the optical filtersto switch from the dark state to the light state, incrementally highervoltages are applied until the device begins to transition from the darkto the light state. In an optical filter made according to the methoddescribed in Example 7 comprising formulation #4 with S001 or S054,fading from the dark to light state is observed at about 1.8 Volts. Thetransitioning is faster at about 2 Volts. It has been observed that toohigh a voltage may not be desirable because other electrochemicalreactions may be introduced that may cause fouling of the electrodes.For example, transitioning in the optical filter is impacted when avoltage greater than about 2.5 volts is applied, and brown spots areobserved if the optical filters are left at that potential for a longerperiod of time.

Example 15 Impact of Optical Filter on Electrical Consumption and CO₂Emissions

The ability of a variable transmittance window of the present inventionto provide significant energy and cost savings was determined. Abuilding with variable transmittance insulated glass units was modeledusing window and energy modeling software available from LawrenceBerkeley National Laboratories of Berkeley, Calif. The building modeledwas a 400 square foot small office with a 0.9 wall-to window ratio. Thebuilding was modeled in five U.S. cities (Miami, Los Angeles, New York,Houston, and Chicago). The variable transmittance smart window used forthe model was an insulating glass unit (IGU) with an optical filterlaminated onto one of the panes, and a low emissivity coating on theinside of the exterior pane facing the sealed space. A variabletransmittance window of this configuration was determined to achieve asolar heat gain coefficient (SHGC) of about 0.15 in the dark state, andabout 0.32 in the light state. Using this variable transmittance windowin the dark state resulted in average electricity savings of 28%,according to the model. The electricity savings resulted from a reducedrequirement for air conditioning due to the variable transmittancewindows. CO₂ emissions were reduced from about 19% to about 25%, duemostly to the reduction in electricity usage. The variable transmittancewindow of the model achieves a solar heat gain coefficient (SHGC) ofabout 0.15 with a corresponding percent visible light transmittance(VLT) of about 10% in the dark state. In the light state, the percentvisible light transmittance of the variable transmittance windowincreases to about 58-60%, and the solar heat gain coefficient increasesto 0.32. In the dark state, the variable transmittance window has asignificantly lower solar heat gain coefficient than standardlow-emissivity (“Low-E”) glass. Standard Low-E glass in the same modelachieves an SHGC of about 0.36, with a VLT of about 60-62%. Standardfloat glass (no coatings) in the same model achieves an SHGC of about0.68, with a VLT of about 68%. Solarban 70XL Glass from PPG Industries(Pittsburgh, Pa.) in the same model achieves an SHGC of about 0.47, witha VLT of about 47%. The standard float glass has the highest (worst)solar heat gain coefficient while Solarban 70XL glass has the best SHGCof the non-dynamic glazings. The SHGC of an IGU using standard floatglass is about 0.70 (according to the dataset included with thesoftware). The SHGC of an IGU made using the Solarban 70XL glass isabout 0.25 (according to the dataset provided with the software). Themodel demonstrates that an SHGC of less than 0.25 can be achieved withvariable transmittance smart windows and dynamic glazings. In thisexample, the modeled variable transmittance window was assumed to have acontrast ratio of about six.

Example 16 Intermediate States of the Optical Filter

A prototype device made using formulation #3 comprising S001, S002 orS042 was tested for the ability to achieve intermediate states. Thedevice is first darkened under UV light (365 nm) although solar lightcan equally be used. A DC voltage of about 2 Volts is then applied tothe device for a short period of time (e.g., about 10% of the totalswitching time) before being switched off. During the time the power isapplied the VLT of the device increases, but did not go all the way tothe light state. Once the voltage is switched off, the device remains inits intermediate dark state without the need for any further applicationof power. If the voltage is turned on again, the device continues totransition to its light state.

Example 17 Photostability of Chromophores in Switching Materials of theOptical Filter

The photostability of chromophores m various combinations of theswitching material is tested by exposing the combination to UV lightsimilar to the UV light in the solar spectrum. Optical filterscomprising the combination are tested at regular intervals to determinedegradation. When the contrast ratio of a device drops to 50% of theoriginal contrast ratio (determined prior to testing), the device isconsidered to have failed. The photostability of an optical filtercomprising the combination is determined using a QUV or QSUN acceleratedweathering tester from Q-Labs, or an S 16 accelerated testing instrumentfrom Solar Light (SL) to test the photostability of the combination athigher power densities.

Chromophores were tested in combination with various switching materialcomponents prepared according to Examples 5 and 7 and the results areshown in Table 4 below. Each chromophore was capable of achieving 700hours in at least one of the combinations of switching material before50% degradation was reached.

Table 4: Formulation and flexible devices tested. All devices employedEnergyFilm™ UV blocker applied externally, save for Device #26. Device25 included an additional acetate layer. All devices employed OC50substrate Device #2 (graphene substrate). PB-50 nm layer of Prussianblue electrochemically deposited on electrodes.

Device Formulation Thickness Chromophore avg int Failure No. Size (cm)(μ) (%) Polymer (%) Solvent Electrolyte (%) Additives method (mW/cm2)(hours) 1 1.5 (ø) 60 S001 (3) PVB (25) Triglyme SL 120 438 2 1.5 (ø) 60S001 (3) PVB (25) Triglyme SL 130 288 3 1.5 (ø) 50 S001 (3) PVB (25)Triglyme SL 110 255 4 1.5 (ø) 60 S068 (3) PVB (25) Triglyme SL 110 191 59 × 6 50 S054 (3.5) PVB (25) Triglyme QUV 9.8 1537 6 2.5 × 2.5 50 S068(20) PVB (25) Triglyme QUV 9.8 1130 7 9 × 6 50 S054 (3) PVB (25)Tetraglyme TBAPF6 (1) QUV 9.8 1073 8 2.5 × 2.5 50 S068 (15) PVB (25)Triglyme QUV 9.8 1037 9 1.5 (ø) 50 S054 (3.5) PVB (20.2) Triglyme TBAPF6(1) HALS A SL 95 104 10 2.5 × 2.5 50 S068 (10) PVB (25) Triglyme QUV 9.8901 11 1.5 (ø) 60 S001 (3) PVB (25) Triglyme QUV 9.8 865 12 1.5 (ø) 50S054 (3.5) PVB (20.2) Triglyme TBAPF6 (1) SL 110 76 13 3 × 5 50 S054 (3)PVB (25) Triglyme PB QUV 9.8 837 14 9 × 6 50 S054 (3) PMMA (25) TriglymeQUV 9.8 801 15 9 × 6 50 S054 (3) PEMA (25) Triglyme QUV 9.8 794 16 9 × 650 S054 (3) PVB (25) Triglyme QUV 9.8 787 17 1.5 (ø) 60 S068 (3) PVB(25) Triglyme QUV 9.8 772 18 9 × 6 50 S054 (3) PVB (25) Tetraglyme QUV9.8 636 19 9 × 6 50 S054 (2) PVB (24) Triglyme TBAPF6 (1) QUV 9.8 608 209 × 6 50 S054 (3.5) PEMA (25) Tetraglyme TBAPF6 (1) QUV 9.8 586 21 2.5 ×2.5 50 S068 (5) PVB (25) Triglyme QUV 9.8 572 22 9 × 6 50 S054 (3) PMMA(25) Tetraglyme QUV 9.8 543 23 3 × 5 50 S054 (3.5) PVB (25) TetraglymeTBAPF6 (1) PB QUV 9.8 522 24 3 × 5 50 S054 (3.5) PVB (25) TetraglymeTBAPF6 (1) QUV 9.8 522 25 3 × 5 50 S054 (6) PVB (22) Triglyme TBAPF6 (1)Qsun 5.6 688 26 7.5 × 7.5 50 S054 (5) PVB (25) Triglyme QUV 9.8 386 27 9× 6 36 S054 (1.5) PVB (24) Triglyme TBAPF6 (1) QUV 9.8 358 28 9 × 6 25S054 (2) PVB (24) Triglyme TBAPF6 (1) QUV 9.8 293 29 2.5 × 2.5 50 S068(2.5) PVB (25) Triglyme QUV 9.8 136 30 9 × 6 50 S054 (1.7) PMMA (25) PCQUV 9.8 64 31 9 × 6 50 S054 (3.5) PVB (25) GBL QUV 9.8 21

Other Embodiments

The present invention has been described with regard to one or moreembodiments. However, it will be apparent to persons skilled in the artthat a number of variations and modifications can be made withoutdeparting from the scope of the invention as defined in the claims.Therefore, although various embodiments of the invention are disclosedherein, many adaptations and modifications may be made within the scopeof the invention in accordance with the common general knowledge ofthose skilled in this art. Such modifications include the substitutionof known equivalents for any aspect of the invention in order to achievethe same result in substantially the same way. Numeric ranges areinclusive of the numbers defining the range. In the specification, theword “comprising” is used as an open-ended term, substantiallyequivalent to the phrase “including, but not limited to,” and the word“comprises” has a corresponding meaning. As used herein, the singularforms “a”, “an” and “the” include plural referents unless the contextclearly dictates otherwise. Citation of references herein shall not beconstrued as an admission that such references are prior art to thepresent invention. Citation of references herein does not constitute anyadmission as to the contents or date of the references. All publicationsare incorporated herein by reference as if each individual publicationwas specifically and individually indicated to be incorporated byreference herein and as though fully set forth herein. The inventionincludes all embodiments and variations substantially as hereinbeforedescribed and with reference to the examples and drawings.

It is contemplated that any embodiment, aspect, example, method,composition, or element discussed in this specification may beimplemented or combined in any suitable manner with any otherembodiment, aspect, example, method, composition, or element.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as is commonly understood by one of ordinary skillin the art to which this invention belongs. If a definition set forth inthis section is contrary to or otherwise inconsistent with a definitionset forth in the patents, applications, published applications and otherpublications that are herein incorporated by reference, the definitionset forth herein prevails over the definition that is incorporatedherein by reference.

1-54. (canceled)
 55. A variable transmittance optical filter comprising:a) a first layer comprising a first substantially transparent substratewith a substantially co-planar (SC) electrode system disposed thereon,the SC electrode system made of transparent electrically conductivematerial and comprising at least one pair of electrically separateelectrodes arranged in a substantially co-planar manner on the firstsubstantially transparent substrate, each pair of electrically separateelectrodes comprising a first electrode and a second electrode, b) asecond layer proximate to the first layer and comprising a transitionmaterial comprising a compound that is both photochromic andelectrochromic, and that darkens in response to a non-electricalstimulus and lightens in response to application of an electric voltage;and c) an electrical connection system for electrically connecting theSC electrode system to a source of electric voltage.
 56. The variabletransmittance optical filter of claim 55, wherein the optical filterfurther comprises a second substantially transparent substrate.
 57. Thevariable transmittance optical filter of claim 55, wherein the firstelectrode and the second electrode of each pair comprise finger-likestructures and the finger-like structures of the first electrode areinterdigitated with the finger-like structures of the second electrode.58. The variable transmittance optical filter of claim 57, wherein thefingerlike structures the first electrode and the finger like structuresof the second electrode are substantially the same length.
 59. Thevariable transmittance optical filter of claim 57, wherein thefingerlike structures of the first electrode and the second electrodeform a linear or curvilinear unit.
 60. The variable transmittanceoptical filter of claim 57, wherein each of the interdigitatedfinger-like structures of the first and second electrodes have aninterdigit spacing of from about 10 μm to about 1 mm or any amount orrange therebetween.
 61. The variable transmittance optical filter ofclaim 55, wherein the surface area of the first electrode issubstantially equal to, or greater than, the surface area of the secondelectrode.
 62. The variable transmittance optical filter of claim 57,wherein the width of the fingerlike structures of the first electrodeand the finger like structures of the second electrode have a ratio offrom about 2:1 to about 100:1 or any amount therebetween.
 63. Thevariable transmittance optical filter of claim 57, wherein the spacebetween the fingerlike structures of the first electrode and secondelectrode is less than the width of the second electrode.
 64. Thevariable transmittance optical filter of claim 55, wherein the firstelectrode is a cathode and the second electrode is an anode.
 65. Thevariable transmittance optical filter of claim 55, wherein the firstelectrode is an anode and the second electrode is a cathode.
 66. Thevariable transmittance optical filter of claim 55, wherein the compoundthat is both photochromic and electrochromic is an anodic species. 67.The variable transmittance optical filter of claim 55, wherein thecompound that is both photochromic and electrochromicis a diarylethene.68. The variable transmittance optical filter of claim 55, wherein thenon-electrical stimulus is light, wherein the light compriseswavelengths of about 350 to about 420 nm, or of about 365 to about 420nm, or of about 374 to about 420 nm, or of about 375 to about 420 nm, orof about 380 to about 420 nm, or of about 385 nm to about 420 nm, or anyamount or range therebetween.
 69. The variable transmittance opticalfilter of claim 55, comprising two or more pairs of electricallyseparate electrodes.
 70. The variable transmittance optical filter ofclaim 55, wherein the variable transmittance optical filter is a film.71. An architectural window, automotive window or ophthalmic devicecomprising the variable transmittance optical filter of claim
 55. 72. Amethod of preparing a variable transmittance optical filter comprisingthe steps of: a) providing a first layer comprising a firstsubstantially transparent substrate, and; i. etching into a layer ofsubstantially transparent electrically conductive material disposedthereon a substantially co-planar (SC) electrode system, the SCelectrode system comprising at least one pair of electrically separateelectrodes arranged in a substantially co-planar manner, each pair ofelectrically separate electrodes comprising a first electrode and asecond electrode; or ii. printing onto the first substrate asubstantially co-planar (SC) electrode system using a conductive ink,the SC electrode system comprising at least one pair of electricallyseparate electrodes arranged in a substantially co-planar manner, eachpair of electrically separate electrodes comprising a first electrodeand a second electrode; b) disposing a second layer proximate to the SCelectrode system, the second layer comprising a transition materialcomprising a compound that is both photochromic and electrochromic thatis capable of dynamically varying the degree of visible lighttransmittance on application of an electric voltage; and c) providing anelectrical connection system electrically connecting the SC electrodesystem to a source of electric voltage.
 73. A method of transitioning atransition material comprising a compound that is both photochromic andelectrochromic from a dark state to a faded state comprising the stepsof: a) applying a positive voltage to a first electrode and a negativevoltage to a second electrode; b) reversing the polarity of the voltage,thereby applying a negative voltage to the first electrode and apositive voltage to the second electrode.
 74. The method of claim 73,wherein the voltage applied to the first and second electrodes is fromabout 0.5 to about 3.0 V, or from about 1.2V to about 2.5 V, or fromabout 1.8V to about 2.2 V, or any amount or range therebetween.